I found Wiki for PSX format, but not PC, and it's very different. The battle models are split into multiple files. For example, for Cloud, the files are named rtaa, rtab, rtac, etc. Apparently the animations are always in xxda (e.g. rtda for Cloud). But it's not clear to me yet how to determine which of the files are vertex data vs. texture data vs. etc.
I guess I could try to re-reverse-engineer it, e.g. by comparing PC vs PSX. But if there's anyone that has info or code or any insight, it would help a lot.
BTW, I have found 3 tools that can read battle model data: Ifalna, Leviathan, and biturn. But I can't find source code for them. Bleh.