The OBB contained a number of files. The bin file is only a few MB larger than the PSP version's.
This leads me to believe the updated sprites are kept in g2d.dat
G2D.DAT's header is YOX, which I haven't seen before.
I believe this is another archive format, rather than a graphics container, because there are multiple points in the file that start with YOX.
Opening of original Post:
Edit: It was a fat32 filesystem and I needed to mount it with Imdisk to open it.
I've been attempting to extract the graphics from the android version of FFTWOTL, but have hit a road block.
The header has a fat32lib label, but unlike another thread I found with a similar issue, it's not openable like a regular archive.
It's also not openable with pre-existing FFTWOTL psp tools or scripts, at least from what I've tried.