Nope but I would say this would be a case-by-case situation. One local gym has an Aussie brown belt with a 3 or 4th Dan Judo instructor from Japan and he naturally went up the belt ranks quickly. Not sure whether it's 2 years but I'd say around that if memory serves.

If they are not trying to win an IBJJF worlds or Pans medal at blue belt then it doesn't matter.

What's the rush?

I agree. no rush at all

If someone is absolutely ready for the next level and there are also no other reasons to hold them back. Holding them back is a bit selfish as it only limits there opportunities for better competition and growth which will help them improve if they are competing and don't care about sandbagging at their current belt for medals. If they are some prodigy that wants to win worlds at every belt then so be it but that is an ultra rare scenario.

If there's no doubt about it then you shouldn't have any doubt yourself.

If you have doubts then maybe there is a reason why you haven't yet and maybe they do need more time.

In my experience minimum requirements are there for a reason. Rushing people in the long run gets them hurt. Seen it too many times. Mat time is important in creating a true understanding of technique and why a technique works, without the need to make it work through athleticism. A really good coach can see the difference between and athlete and a tactician making a technique work.

In my experience waiting only tightens the belt around students waist when the belt is tied, and they can move on knowing they are truly that rank.