The main reason 100% isn't really a thing is because it would be a ludicrous category to run assuming it uses the conventional 'everything in the pause menu' definition, mostly due to collecting all the catch cards, which would not only make the run stupidly long, but also add a huge element of RNG since you can get a lot of the cards through buying card bags which give you a random card. I imagine it could be added if someone really wanted to run it, but I don't think anyone has expressed much interest in actually running it.

Hi, I'd like my name changed to "imdead" if that's possible

Thanks

Yes, you start counting as soon as you hit A to run away, and you jump on the 13th beat. Also, one thing I forgot to mention is make sure you're not mashing A to get the spin jump; you need to hold A for a few frames in order to get max height out of the jump. You only want to hold it very briefly, but you definitely don't want to mash.

If you do really want to incorporate it though, I can say it also helps to practice landing on the platform by jumping on the bench in the blimp area behind west rogueport, but note that the distance from the ground to the top of that bench is equal to the distance from the top of the platform for Yoshi skip between the max height you can get from a jump off the bottles, so a spin jump is often required for the real trick. It still helps a lot in getting the muscle memory for landing the second jump though, and the method I use is hold up then immediately straight left after you jump, though some use up then up-left, and an older method uses down then down-down-left (in between down and down-left), but I've found up then straight left to be the most consistent for me.

Even with all this though, the trick is still super difficult and I don't think anyone is very consistent at it yet, so if you are starting out and really don't want to deal with this trick, that's perfectly reasonable, it only saves up to ~10-14 minutes with good execution, so you aren't doing a drastically different route. The downside to skipping it though is chapter 3 RNG can be a pain, and you'll need to learn the JP conditions if you don't know them, which you can find images for on the resources page.