The last time I was at DVSI, two years ago, my experience mirrored the OP's, except for the hounding to attend a presentation. I arrived early at 3:30 (had left home early to beat the traffic). Room not ready at 4:00. Waited in the lobby. Room still not ready at 5:00. Waited some more. Approached the desk again at 6:00 when they still hadn't texted me. They called housekeeping, which said the room was ready. In my feedback to the resort, I noted the crappy check-in experience I had.
Although that's the first time I experienced such a lame check-in at DVSI, it has happened to me numerous times in the past when visiting Westin Desert Willow. Over many years, I don't think I ever got my room anywhere close to 4:00 or 4:30. I always just accepted it as the norm.
I'm going to be at DSVI again a week from now, and at WDW next month. Now I realize, from the posts above, that if this happens again, I should request and expect compensation for unreasonable delay and lost hours that I paid for. When they say check-in is at 4:00, they need to honor that.