Devil's advocate - if for some reason you're using "while(<constant evaluating to true>)" to do something other than wait for some kind of event, and if whatever you're doing is fast but repeated a huge number of times, it's possible that you'd see some speedup in the overall program by using a "faster" conditional evaluation (assuming that it's actually evaluated at runtime and not compiled away because it's a constant value).

I am having a really, really hard time contriving a reason for this, though. It may be my lack of imagination, but I feel like the only reason this would come up is if you deliberately designed a system specifically to make this an issue.

Honestly, you could take this question a bunch of ways. Maybe he's just trying to ask about whether the speed of a cast-to-bool depends on the value of the thing you're casting, maybe he's trying to get you to see that the compiled code won't even evaluate the conditional at runtime anyway or maybe he's trying to get you to realize that you'd almost certainly not care because even if it were evaluating the conditional, if you're using while(<true>), you're almost certainly waiting for some event, so the only thing it could possibly affect would be polling speed, negligibly.