No one knows if it was due to someone checking out late. 4pm is more than acceptable when the checkin time is 3pm. Stuff happens. Maybe some of the staff was out sick and the poor CM was stressed.
Stuff happens, but an apology would have been nice rather than a rude response. I don't care how stressed you are, if your job is to deal with the public, there's no need to be rude.
Did we complain, demand compensation or write a letter about the late check-in? No. We just grumbled about it a bit to ourselves and I mentioned it in my WL review when we got back. It didn't ruin the trip but it was a bummer way to start out-- we had ADRs at Cape May that night, so we were unable to actually see and get into our room until 7pm or so. We had been hoping to freshen up a bit before dinner.

(sorry, i couldn't resist)
I simply posted an experience I had about check-in time when it came up in conversation.