[duskwuff]

> I'm wondering if the artists still used the sheet system, but a memory optimizer tool re-ordered the tiles to help free up a little more space on the ROM.

Seems unlikely. Managing the "physical" layout of sprites on a sheet is a lot of work; there's no reason to do that if it's going to be thrown out by an optimizer in the end.

Besides, notice that, on the optimized SF2 sheet, all of the tiles for one sprite get written out in order; they aren't interleaved left-to-right like the tiles would have been on a sheet.