yeah, the YRotN is used for a few animations here and there, but it's mostly used for other things, like it's the bone that the tag points to (the P1 or CPU or whatever it is thing). but it's not going to cause glitches (that i know of) if one isn't there.
but it's as i thought, as Gamma pointed out, the ThrowN reference was off, which is why the freezing would occur.
and Gamma, i figured that it would corrupt. i added bones to a model that had 10 bones, and it could only take up to 41, but a model with 11 took up to 56. try putting enough bones in to the point that it won't take any more (for 4 bones, it's probably only 20-30), and then put it over Beast Ganon, and try it in game. if it freezes when you try to use the final smash, then it won't work. my theory is that it won't work, but i've only tested that on fighter characters, so i'm not sure if the bone limitation is a universal thing or not. try it and report back.