I'm going to be honest. As far as Sonic's rolling physics, I don't really think losing speed when going uphill actually contributes anything meaningful to the game besides being "realistic," and when I see someone criticize a game for lacking this particular aspect to the degree it "should" (like for example, Freedom Planet), I can only really wonder what all the fuss is about. The only time it actually affects my gameplay, the only time it's a thing I kind of, SORT OF think about, is if for some reason I don't have enough speed to overcome a momentum based obstacle to where I can just hold right to automatically overcome it. And in such cases... All you need to do is just go back and charge up a spindash, which is nothing. There's no skill, thought, or real consequence there. I know people say that the spindash isn't that spammable because you need to be standing on level ground and because you sacrifice control. But thinking about the actual level design of these games, I'll say it once again: I can't think of a single instance where you need to use this to overcome a momentum based obstacle where either of those things are actually a problem. There is level ground right before these obstacles in every case I can think of, so finding it so as to use it is not going to be a problem at all. And when you need to overcome a momentum-based obstacle, they don't generally design these levels where spindashing through them will rob you of the control needed to deal with what's coming up in the level. Not in well-designed levels with good conveyance, at least. Outside of like speedrunning, in which case there are a million other more interesting things to think about and optimize than this, the only thing that losing speed uphill actually contributes is being at most a minor annoyance that sort of disrupts the flow to a very small degree. I can think of ONE exception. And that is Sonic Advance 3. Some of these momentum based obstacles, some of these ramps are SO TALL that the only way to have enough speed to overcome them is if you're Sonic, because he has much higher top speed and acceleration than others in that game. That's it, my guy.