I maintain that I had no such issues half-piping in STH4. I really, truly, have no idea what STM is talking about on that one.
Beat the game today. Final boss is annoying as hell in FIGURING OUT what to do, but easy once you know how.
Ring collection in the ending jog could not possibly be more pointless. Seriously, I nabbed all the Chaos Emeralds, blew up all the machines, and Eggman is laughing at me because I had less than perfect jumps in an auto-run devoid of enemies or hazards? Riiiight.
The one stunt which I didn't feel worked well was the vine-swinging, but thankfully that was limited to a single Act (and in most cases you can find an alternate path). Timing on the jumps from a swing just felt too strict, or maybe it has something to do with how you hold the D-Pad, I dunno.
Every example in that video I can attribute to either You're Doing it Wrong or You're Doing it on Purpose.
Obviously true on the incline deceleration. ANY seasoned Sonic player, when they see they are not clearing an incline (and yes that can happen a plenty) will either turn around or jump, and jumping off of an incline was never smooth in the Genesis games to begin with (if anything Homing Attack gives you more of a fighting chance in those situations).
Air physics were done on purpose to demonstrate the point, and while 3D Sonic has gotten me in the habit of holding forward, you do have to get VERY strict about it in STH4. And, obviously, it throws off your ability to land until you process how it works. It doesn't take long, but that particular bump is simply inevitable. It's just not the way any previous 2D Sonic ever handled.
And maybe it's just me, but even in the Genesis days I held forward after a spin dash, or most anything that requires me going forward at all, so the air momentum thing is not a problem to me. Hell, stopping in mid air could actually be very helpful when platforming. You can fall at the precise spot and not worry about overshooting.
I actually notice it more when trying to brake from a spin-dash, particularly during the final boss fight, so yeah it can be useful once you adjust. But really, a Homing Attack/Jump Dash in the opposite direction ought to be able to cancel momentum just as well without screwing with the default movement. Further, if we're open to incorporating 3D Sonic abilities into 2D (and I must admit they handled that pretty well; felt a lot more natural than midair boosting in Rush, and the range was short enough that it didn't break the game), I think a MANUAL Jump Cancel such as used in Secret Rings/Black Knight wouldn't have been a bad idea. Heck, there were a few areas in the final Act where I would have killed for such an ability, what with how fast those freaking gates close. Come at one too high in the air and you're dead.