This is confirmed. You can no longer play as a Yeti in Yeti Hunter. If you pick Prefer Yeti, you always get Hunter.
It doesn’t happen to everyone. If literally everyone were getting put in the Hunter queue, we’d all be getting Yeti 1/6 games on average. For whatever reason, some players seem to be getting put in the Hunter queue no matter what, and since so many people are queuing Yeti for the spray, it’s extremely unlikely to get Yeti from Hunter queue.