Ronrosa,
Hi, and welcome to the boards.
Regarding your question, and based only on my 3 trip to Coz experience, diving with Dive House: usually the dive masters send up buddy teams when either gets low on air-up to the predetermined time limit, when the remaining divers come up as a group. The other situation occurs when a group of divers, with similar air usage ascend as a group. The current is in many cases not a factor, because the dive boats "follow bubbles"-at a safe distance, and come in to pick up each buddy team as they surface.
If you and your buddy have significant air consumption rate differences, you might consider mentioning this to the DMs-they may suggest a different buddy pairing so that you can get the max bottom time possible, or they might "re-buddy " you up if your (travel) buddy, and someone else get low on air at the same time.While these scenarios depend on chance, they might work out. Given the vis in Coz,you won't have a problem staying with your "non-buddy buddy" .
Any body else have different experiences with different operators?
Good luck,
Miked