I'm not sure what that is supposed to mean in this context. Testing for "is not None" is more explicit and avoids the trap being discussed. I don't know how the second sentence applies, maybe "if timeval:" is simpler?
BTW, do you know the original author of the Zen of Python has posted to this very dicussion (while also being the orginal author of said module):
"Simplicity" is not measured in terms of key presses or characters.
The "if timeval:" case may contain fewer characters, but it's less explicit. Being less explicit opens it up to greater ambiguity. Ambiguity is a form of complexity. Complexity is the opposite of simplicity.
The explicit "is not None" check may require more typing, but it's far more explicit and exact. That means it's much less ambiguous, and thus less complex, and thus exhibits greater simplicity.
Simple is better than complex.