It doesn't really have anything to do with policy or working odd hours. Unless everyone presses enter at the same time, grades will be input at different times. (I'd love to see administrators trying to corral senior faculty into doing that, though.)
As to whether a system should process grades more than once a day, that's obviously a judgement call that Columbia has made. And as someone who worked in the administration of similar university, a small part of me is cheering on whoever at Columbia has held fast against the demand for up-to-the-minute GPAs.
Actually, so you're saying you think it is all the result of smart policy, and I agree with you now. I see that up-to-the-minute GPA's are a real burden. Funny though, that they all have to hit enter at the same time, didn't realize it was that brilliant. ;)
As to whether a system should process grades more than once a day, that's obviously a judgement call that Columbia has made. And as someone who worked in the administration of similar university, a small part of me is cheering on whoever at Columbia has held fast against the demand for up-to-the-minute GPAs.