Great. You told me what Trevor's vspeed is when he jumps. Now tell me how it's CALCULATED. And it doesn't just go -5,-3,-2,-1,0,-1, 0 (yes, I noticed that too and there's a reason). It will go -5 for a couple steps then -3 for a couple steps then -2 then -1. And as for why it goes -1,0,-1,0, that's when vspeed is -2/3, -1/2 or -1/3 (I forgot which speeds are used). Trevor follows a calculated parabolic function. And those floating platforms -- both the ones that bob vertically and the ones that move side to side -- also follow parabolic functions. Or maybe the term is sinusoidal. Either way, the movement isn't "uniform" and either Konami plotted it all out on graphs and then hard-coded the movement like I did in GMvania or they knew how to plot sinusoidal movement with whatever engine they were using. Reading the ASM will tell you exactly what's going on, what processes led to those values of -5, -3, -2, -1, 0, -1, 0. Sometimes it really is just a simple hard-code, like the player name encryption, but a lot of times there's some mathematical function yielding those values followed by a series of branch checks. If you want numbers for Trevor, Axe Knights, Skeletons or Medusa Heads, just open GMvania and read through the timelines. But what I want are the formulas Konami used to get those numbers.
And when you're dealing with bats and crows, that's a whole other royal pain in the fucking ass.