Sure . . . just like many games in MAME don't work until someone fixes the sound or whatever. I understand that the 360 isn't 100% backwards compatible, but it's also not as though MS has to write a new emulator for each game. They wrote exactly one emulator. Just by flipping the switch to "on" (figuratively speaking) they probably had tons of games running, many at 100%. Then they went through and found games that weren't running at 100% and if they were popular, the emulator was tweaked so that it would run those games. This is, of course, a gross simplification of the process, but you understand what I mean.
Oh . . . and I should point out that I was unaware that the 80 GB version still had a PS2 hardware component inside helping with emulation duties before you posted about it in this or another thread. I suppose that probably does foreclose the possibility of backwards compatibility ever showing up on the 40GB PS3 or any others built around that hardware. Technically possible, of course, just like it's done on 360, but realistically, the demand for the feature is probably not all that great.