That's cool. I am the author :) . Actually I submitted a direct link to the search a month ago, but didn't get any upvotes. So I'm happy that I got some now with the write-up :)
Yes I haven't optimized a lot for older hardware, but I think it could definitely be done, just have to ditch the complex stuff I am using to scale to high number of units when there are not many of them.
The models have about 1k triangles each. The code is optimized to scale to many units (racers), but the initial rendering cost of instancing with pre-rendered animation skeleton may be high I suspect, so it may be slow for few units on old hardware. I could try to have different rendering paths for small and big number of units to alleviate the problem.
I used the website, downloaded the mp4 and postprocessed to walk in place using a shell script: https://github.com/emnh/mantary-platformer/blob/main/animscr...
The character was generated using stable diffusion.