I haven’t heard anything about it, but my theory is that, at the beginning of each round, players are put into groups based on either past scoops or past medals of either the last round or all previous rounds. The groups are then separated into sub-groups, which are the domination teams we see, and as each player in a category get a scoop, they are placed into one of the sub-groups, ostensibly in the sub-group that has the fewest members.

My theory, anyway. I’ve heard others.