If the expectation is just hours worked, then you can't fulfill 2 (or more) full time jobs. But I'm not sure where that applies, outside of something mind-numbing like a call center.

Realistically, it's a technical field and there are a lot of very, very poor candidates out there who will fill the seat for 40 hours but completely fail on performance. And I think that's why nobody was judging performance based on hours of butt in seat.