Making an argument does in and of itself prove anything. So you have, in fact, proven nothing. You don't know what the collision sizes on the attacks in the game are. You're making a lot of assumptions about what's programmed into the game before it's even out. They could do all the things you mentioned, but the facts are we don't know that they're doing that.
My comment about collision boxes was a hypothetical, not a proof, but if you want to go there, based on common sense, history, and gameplay videos, I would bet a sizable sum that the collision boxes are exactly as I predict.
And a proof is an argument. You said taking out ducking gives the player less functionality, but the issue with that is the game replaces it with at least two other functions, making your statement false.
You're putting words in my mouth. I never said ducking was better or worse a design choice than blocking & rolling. I'm saying not having it takes away from the game's potential and moves it farther away from the rest of the 2D games in the series, nothing more.
"Takes away from the game's potential". Qualitative value judgement right there.
Any time you give the player more ways to maneuver their character it makes for more interesting and varied game play. Playing the end product that would presumably be design specifically with the lack of a crouch in mind will prove what exactly? You can't prove or disprove a hypothetical game mechanic's worth by playing something that isn't designed to include it. That makes no logical sense at all.
So you get it, but you don't get it.
Games are about function, not form. To that end, maneuvers posess no intrinsic value. Adding ducking serves no purpose, makes nothing more varied and interesting, unless it is given one within the game.
Take Sonic the Hedgehog, for example. The games have ducking, but it there are few situations in which ducking allows you to dodge an attack, and does little more than add an unnecessary motion that needs to be done before rolling. You could map the dash roll to its own button, and nothing would change. Nothing would be more varied and interesting.