If a candidate says they are 'never' willing to work overtime, they are probably in the wrong business. I can't say I've ever had someone tell me never. Most engineers understand that there are going to be at least some support or production situations that need to be addressed beyond standard biz hours. I wouldn't say that is passion or commitment - having some expectation of at least occasional overtime is probably just a minimum requirement.
There is a good chance the candidate has been burned in the past by too many instances of 'the sky is falling' or 'I need this tomorrow for no good reason' types of overtime and isn't willing to be taken advantage again.
I haven't really ever been required to work overtime but I've always emailed my boss before I left for the day to ask if there was anything else he needed before I took off for the day. I don't want to work overtime, or like it, but will if something needs to be done. I don't like the culture where everyone sits at there desk for an extra 15 minutes because they are afraid to be the first one to leave.
Overtime should be reserved for emergencies, not for demonstrating passion or commitment.
Just to clarify, if someone stayed late to fix something on Tuesday and then clocked off early on Wednesday in lieu, would that count as overtime in your definition?
