If you're on a desert island and you have 2 watches instead of 1, the probability of failure (defined as "don't know the time") within T years goes from p to p^2 + epsilon (where epsilon encapsulates things like correlated manufacturing defects).
So in a way, yes.
The main difference is that "don't know the time" is a trivial consequence, but "crash into a white truck at 70mph" is non-trivial.
It's different because the challenge with self-driving is not to know the exact time. You win for simply noticing the discrepancy and stopping.
Imagine if the watch simply tells you if it is safe to jump into the pool (depending on the time it may or may not have water). If watches conflict, you still win by not jumping.
