I think Super Circuit was developed on prototype hardware and then rushed out to be as close as launch as possible (it wasn't a launch title but very early on). There might be a technical reason why it doesn't run on 60fps. Nicktoons Racing had an extra year.

Then again considering how shortlived they were, Crawfish did do some technical achievements. Playable versions of Street Fighter Alpha (GBC) and Alpha 3 (GBA), an early GBA FPS that somehow was better than the movie itself (Ecks vs Sever) and would have done a decent version of a GTA game if it wasn't for their closure. Publishers really screwed them over...

The fact that this game consistently runs at a smooth 60 fps and Super Circuit does not will never not be funny