Jaguar isn't 64-bit really, but that doesn't matter.
The system has five programmable processors as its entire architecture. It's also riddled with flaws and bugs, making it much harder to emulate "correctly".
Saturn, for comparison, has three "programmable" and three fixed, and only just got emulated correctly.
N64 only has two. :flowers: One of them, the Reality Coprocessor, IS programmable, and tends to cause massive problems in the few games that abused it severely (Resident Evil 2).