It might be able to, but it doesn't know the state of the system. It could try to determine that somehow, but that would complicate the watchdog a lot, and that

It might be able to, but it doesn't know the state of the system. It could try to determine that somehow, but that would complicate the watchdog a lot, and that is code that is almost never exercised, so the chance that there would be bugs in that code is much higher. If shutdowns were more frequent, a crash-only design might indeed have made more sense.