MostlyHarmless42
Adventurer
As I said, as a DM I would allow it, and as a player I would love it!
It makes the strong brutish rogue more viable because with good STR and Athletics, you could knock and opponent prone and then bonus action sneak attack. And frankly, is that a pretty good tactic when fighting IRL, to get your opponent to the the ground?
So, yeah, I completely agree it isn't RAI, but I think is better for the game to allow it than worse.
Ironically, this is how one should actually fight someone in platemail if you don't have a war hammer (which was designed to dent armor). Additionally for those with gauntlets there was a technique called "half-swording" where they would hold the blade and use either half the blade as a stabbing device to aim for armor cracks or use the hilt/guard as a hammer. Most "noble knights" would just knock each other down and slit the other's throat with a dagger. Of course any historian knows the real way time beat your opponent is to unscrew your pommel and end them rightly!
My favorite two scenes from early Game of Thrones (back with the show still gave a damn about quality writing) are the duel the character Bronn has with the knight of the veil where he tries him out by dodging and weaving, then goes into finish him off, and the scene where the Hound tells Arya to go ahead and stab him with Needle and it doesn't work.
Want "real" armor rules in your game? Scrap the whole ac model short of adding dex to dodging and use DR with heavy armor outright negating slashing or piercing weapons and requiring a time limit/con saves/checks before someone can't move in combat due to exhaustion. Anything else is "fantasy/game bs". I'm totally fine with the AC system, but will never defend it as "realistic".