Only once had a late checkout request denied, and this was pre-covid at a Hyatt Regency. I pointed out the programme terms and was told that the hotel was a resort and they needed the room back before 4pm. Checked the list of resorts and it was not.

Asked for the denial of late check out and the reason to be written up and emailed to me, so I could follow up with my Concierge. They didn't write the email, but instead granted the late check out.