To be honest, I've never heard of this, and it's quite surprising because it seems like there are privileges for those who can bring lots of players to a casino, and I doubt that really exists, because one of the review websites that can bring lots of players to one casino actually has problems with the system affiliate that the casino provides, so it seems like it doesn't exist unless there is a special collaboration or you as a person who can bring many players to one of the casinos also have access to the casino manager so that they can help when one of the referrals experiences problems with withdrawals or something else.
If that is true, this can be considered a shady activity but it can also be considered a profitable collaboration because the affiliate will be able to confidently promote the casino because there is a guarantee that players who register via the link will get privileges, which will also provide benefits to the casino because many players will play at the casino.