Probable? Not Very

Pope Innocent the third had just launched the largest military operation in medieval Europe not against Muslims not against pagans but against Christians the targets were the Cathars a sect flourishing in southern France but historians analyzing Inquisition depositions note something strange the soldiers didn't just kill heretics they systematically destroyed records Parish books marriage contracts family bibles village registries interrogation transcripts from surviving witnesses describe crusaders demanding not confessions of faith but names of relatives marriage records genealogies going back generations

"but historians analyzing Inquisition depositions"

Why would this note what the soldiers did? The Inquisition was a tribunal, not a newspaper redaction.

Also, it would be very nice to have actual names of actual historians. Not just the word "historians" ...

"they systematically destroyed records Parish books marriage contracts family bibles village registries"

Why not phone numbers while we are at it?

The parish family book (Latin: Status animarum, meaning "State of Souls") is a register of people living in a parish and of events related to them. It is particularly characteristic of the Roman Catholic Church. The parish family books were prescribed in the Rituale Romanum published in 1614 by Pope Paul V. At first, they only contained data about sacraments received, religious knowledge, and religious affiliation. In the 18th century other data were added such as house numbers and ages. The parish family books were maintained by parish priests. They were most precise in villages because the population was more stable there than in cities.

Or a bit older:

In France, parish registers have been in use since the Middle Ages. The oldest surviving registers date back to 1303 and are posted in Givry. Other existing registers prior to orders of civil legislation in 1539 reside in Roz-Landrieux 1451, Paramé 1453, Lanloup 1467, Trans-la-Forêt 1479 and Signes 1500.[13]

The parish register became mandatory in France for baptisms with the Ordinance of Villers-Cotterêts signed into law by Francis I of France on August 10, 1539, then for marriages and burials with the Ordinance of Blois in 1579. They had to be sent every year to the bailiwick or sénéchaussée in the south of France.[14] In April 1667, the Ordinance of Saint-Germain-en-Laye ordered a copy to be kept by the parish clergy as before the ordinance.[15]

German wiki:

Die ältesten Kirchenbücher – sie liegen nur als Fragment vor – stammen aus dem 14. Jahrhundert und entstanden in der Provence und in Italien.

So, in fact, the oldest Parish books were from a century later than the Albigensian Crusade. One cannot totally say "Paul V was nearly as much later as Alexander Graham Bell" because some kind of Church books existed within a century. One could construe this as "well, the Inquisition destroyed the earlier ones" but it is not the most probable scenario, and also, the videast is not backing this up by pointing to actual names of actual historians. But I think I can do one better.

Thought. I recall finding the view in St. Thomas that: a) if a marriage is reputed valid because the contrahents were above 14 for the male, 12 for the female, but b) it wasn't because one of them hadn't reached puberty, then c) instead of seeking an annulment, the contrahent who had reached puberty and wanted to marry someone else should do so elsewhere, where they weren't known. This state was obviously no longer possible to practise once one had parish books, so this would indicate that the system of parish books was not yet put into place.

The same video speaks of "all record keeping institutions" ... in the sense of modern meticulous record, there weren't that many, not even Church parishes.

Right now, I think one should look at if the "Catholic Church" (a k a Vatican II Sect, not identic to the historic Catholic Church due to changes in theology) is scraping inconvenient data from the online versions of St. Thomas Aquinas. I recalled Prima via as including the words "manifestum est et patet sensibus aliquid moveri, utputa sol" (it is obvious and open to the senses that some things are in movement, as for instance the sun), making clear what I also know from Riccioli that St. Thomas was making the daily motion of the universe the clearest example. Here is the translation in New Advent: "It is certain, and evident to our senses, that in the world some things are in motion." No mention of the sun being among them. Because other than the daily one movements of the sun would not be evident to our senses, and heliocentrism holds that the daily one is only falsely evident to our senses, by the "train passenger" type of optic illusion. Unfortunately the guys at New Advent are heliocentrics, as are a lot of clergy of the Vatican II Sect.

Give me a shout-out if you have access to either info from St. Thomas' Summe in some printed Latin edition, please!

"interrogation transcripts from surviving witnesses describe crusaders demanding not confessions of faith but names of relatives marriage records genealogies going back generations"

If you had spoken about the Spanish Inquisition and about Jewish family records, I could have believed you. Especially if it were about a newly become Spanish territory, since an old one would have had the Inquisitors already keeping track of Jewish families. The problem endemic to Spain was crypto-Jews, after 1492. Inquisitors wanted to make sure a Catholic of Jewish family origins wasn't a crypto-Jew. Two Spaniards (or a Basque and a Galego) would agree with me that this was somewhat overdoing it. I've named St. Ignatius of Loyola and Francisco Franco Bahamonde. The founder of the Jesuits and the Caudillo who died when I was a child.

But for the Inquisition or the previous Crusade into Languedoc, this seems off. Armies weren't highly tightly knit networks of discipline, they were pretty loose stuff involving volunteers. I can picture SS taking Jews from Ukraine to certain camps, I cannot imagine the volunteers of Blue Division (from Franco's Spain) doing so. And Medieval Crusader armies, well, they were more like Blue Division than any kind of SS. But this chasing of documents would have been a work for the Gestapo. Didn't exist back then.

Hans Georg Lundahl
Paris
St. Valérie of Limoges
9.XII.2025

Lemovicis, in Aquitania, sanctae Valeriae, Virginis et Martyris.

PS, the videast has taken Fr. Saunière as being a village priest recording marriages as they were held, in the years around 1200, he was indeed a priest, but of the 19th C. The originator of this theory./HGL

PPS, if there was a letter about "pretender lineage" from 1210 it's about the Albigensian Perfecti claiming a lineage from the Apostles, rival to the Roman Catholic claim (with partial sharing with Orthodox and some more)./HGL