Agreed.

Armor historians from the 1960s, all the way back to Victorian age, sat in their offices smoking pipes and imagining what purpose the armor served, and and what constraints molded it.

Then the SCA and Renaissance Faires sprang up, and it was no longer purely theoretical. Recreationist research became a thing. And historical analysis became practical.

The most glaring example are the rectangular epaulets on funereal brasses and sarcophagi. Historian used to claim they were used to deflect blows from the shoulder.

Nothing is flat after a blow. All real armor is built on pressure-spreading arches, often first two-dimensionally, but ultimately in three dimensions (the armor over a 16th-century knight's legs are never conic sections, but more fluid curves).

So, those rectangles? Not defensive metal, but purely decorative, and probably leather or paper-mache. (None survive, and in fact there's some argument they exist only in art.)

Any historian who tried to make one and use it would learn this in a short exercise. But the fallacy survived for decades, because the people were operating outside of their area of expertise, while falsely claiming otherwise with no criticism.

Another example is the still-pervasive myth that medieval people used spice to mask the flavor of spoiled meat; I've heard it used by academics a couple decades ago at a conference presentation. Ever eaten spoiled meat? Ever think to yourself, this bellyache wouldn't be so bad if I didn't taste the source of my poisoning? That myth was tracked back to a singular author in the 1950s, IIRC, and copied without any rational criticism ever since.