yep - my comment there is very simplified, but, I suspect there's effectively a visual shorthand going on - and its not just foreign - its also the chronologically un-christian - so you see the Romans at the crucifixion carrying messers, Goliath (and the philistines) having falchions, Alexander the Great, in biographies carrying them, that kind of thing.

The way I tend to describe it is, its the medieval equivalent of the "black hat" cowboy in the 50's westerns being the baddie - its showing that the owner of these arms isnt a godly, christian knight of the word everyone should aspire to.

Medieval art is a really intriguing research subject as a lot of it is simultaneously very accurate depictions, and incredibly fanciful creations. A lot of people have been dismissing medieval art as entirely unreliable, but, personally, I think they're completely wrong - the question is where its unreliable.
In a way, its a bit like someone from 3020 looking at "independence day" or "Jurassic Park", We, the viewer today know fine well that the alien spaceship or the dinosaur stomping around isnt contemporary. But the F18 jet, or the Land Rover driving along with the dinosaurs? Those are fairly realistic portrayals of real objects. same goes for medieval art - even the strange stuff like marginalia. Yes, that knight is fighting a man-sized snail that's got a rabbit on its back, armed with a lance.... but the lance, and the falchion the knight's holding are both relatively realistic portrayals. There are facets or aspects of the reality which are fabricated, and parts which are entirely viable. The real challenge is dissecting the bits where the lines blur.