I find it funny several took my point as "your oshi isn't doing the work!" when my literal point was Vtubing allows for fill-ins when someone isn't physically capable of doing the work, in direct reference "forever on death's door" Ironmouse. It's also entirely possible a corpo Vtuber is in a wheel chair and we have no clue about it.
For Hololive specifically, they'd only use stand-in 3D tracking if they were in a bind. Idol-types are extremely autistic about certain details, so I'd be very surprised if we ever got any foreground replacement choreo. What would not surprise me is if the big group shots had a lot of mis-matched choreo because database systems can have their days.
As for something like Treasure Box, I think the important thing to also consider is that Auto Tune has existed for approaching 3 decades. It's mostly used to tweak rather than the full T-Pain effect. 3D tracking is far enough along there should be smoothing tools available professionally. For something like Marine's hip sway, it's entirely possible it's actually a blend of her real moves and the choreographer doing it. Thus being blended "in post".
All that said, Korone definitely did that front walk over herself. That's exactly something the doggo would come up with and make sure she could do well. (Ignoring that it might be the single easiest move in all of gymnastics.) Though I have noticed no else but seemingly Fillan, in the Vtuber space, has attempted to use anything like that as part of some show. Probably has something to do with everyone in the sphere being horrible introverts that need to touch grass more.
Well, Sana almost put herself in one, if we take how bad her back was for a while. I was more thinking one of the smaller corpo or a JP Nijisanji member that doesn't get any translated to English run. Fairly certain we've got general proof of all of the HoloMembers being ambulatory. Minus Marine probably needing a cane already.