If they were, the first one was a definite oops - they should have been told to leave their stuff with bell services - probably a training issue. There isn't any reason for late check out for a conference - pack up and drop your stuff off for the day, just like the rest of us do when we want to do something else with our day.
I think we've have heard other cases of letting people stay a little longer when illness is involved.
As to not being cash customers - get used to it. Timeshares work in part because we are each paying for the capacity - it isn't sitting around idle. OP, you won't get a lot of sympathy here for not being allowed late check out because when you don't get out of the room on time, you are using MY TIME in that room. I got off a plane at 11am, I've been up since 4am, and I'd really like to get into my room before 6pm so I can shower before dinner. I know that I'm not likely to arrive at the airport to a text that says I can go straight up - and I plan accordingly - but I get cranky if I haven't gotten into my room before my 7pm dinner reservation. Maybe CMs can state it nicer, but given how dense people are, some of them don't get nice. Blame the people who can't take a hint.
This is different than a hotel, where there is usually about 10% unused occupancy in a well occupied hotel. When hotel occupancy runs as tight as timeshares, they stop allowing late checkout as well.