By time in grade requirements I take it you mean a minimal amount of time a student has to hold their current rank before they're eligible for promotion. For instance, before you can be a black belt you have to be a brown belt for a certain x length of time and only after you've been a brown belt for that length of time are you eligible for the black belt no matter how skilled you might be, minimum time requirements aren't uncommon and those I can understand as long as the minimum time requirement is within reason but as to the student I was referring to in my original post, Im not quite sure that's how it was done at his dojo.
The impression I got was that at his dojo you had to wait indefinitely to promote because the sensei wanted you to be patient. For instance if you were a brown belt working on getting a black belt you would have to wait indefinitely before you could test for the black belt no matter how skilled you might be, all in the name of patience. I could be wrong with my impression but that was just the impression I got from the description he gave.
Anyway, that's what Im against, having to wait indefinitely just because your sensei wants you to be patient. If your sensei does have reasonable minimum time requirements then you should be able to test once you've met those requirements, so if you've been a brown belt for as long as you need to be in order to fulfill the minimum time requirement then you should be eligible to test for the black belt. It's having to wait indefinitely that Im against.