Yes the benefits table does say 2PM but if does also say “subject to availability”.

https://www.ihg.com/content/gb/en/cu...er-tc/2nd-page

I’ve had a couple of 2pm requests polity declined (“but I can manage 1pm if that’s OK?” ) due to how busy the hotel is but I don’t recall been refused a 1pm checkout request.

Often the refusals are dependent on how the request was made but also when it was made. Given the need to prep rooms for the next batch of guests it’s more than likely that some hotels will ration how many 2pm checkouts they can manage in order to manage the housekeepers schedules.