Mattyo said:
https://twitter.com/yoyoyononabeta/status/1300277414581460994?s=20

The scene this layout is from comes just after this cut. Based on the animation, I think it's fair to presume that at least part of this would be Tomonaga, and that he did the end of the A part.

If this is the case, and considering that animators' parts on episodes seem to have been pretty well defined, I don't think that post #154220 is Tomonaga