We are told its 30fps in splitscreen yes. (compared to 60fps fullscreen)
But I thought it was so bad in splitscreen that I question the part about 30fps hehe, but it could be correct.

The game feels a lot slower in splitscreen and its not as smooth on the eyes either, so I guess I would say both slower and "missing frames".

I just played some Pulse on the PSP and turned it off immediately. I will never again be able to play that game. I knew it was bad and this was gonna happen before I even tried WOHD, but now I have experienced it too. =P