The mod is: https://gamebanana.com/mods/391016

Correct me if I'm wrong but it's just a skin for Knuckles and no gameplay mechanics are changed, if so then it won't be accepted, as mods need to put a unique spin on the speedrun to be considered.

This video has the attack in it:https://m.youtube.com/watch?v=aapdne5QN8Q&t=7s

Having tried the mod myself, I'll be completely honest: it's fun content, it's unique, but it's just Knuckles with a quick-drop animation and slightly higher jump. Although it is not a sprite-swap, it's a full-on character.

There's huge potential for accidental glitches - you can glitch through non-solid terrain (like bridges) using the "quick drop" move - but in general it doesn't seem to offer much more in terms of diversity vs what Knuckles offers.

Marble garden is broken with it

It seems like there are some lacking sprites

I hope that doesn’t count it down in any way