Just as a data point at Fort Lauderdale last week they didn't check anything for me. We checked in 45 minutes before our assigned time, at 10:45, and were held in a room briefly as they let The Key passengers board, then after The Key people were all the way on the boat, we were let on. I didn't check my watch but I'm sure we were all on the boat before 11:15 (vs. our check in window of 11:30-12).
I didn't see any other Fort Lauderdale posts in the thread so I thought I'd share.