I just got my confirmation for OKW for next May. It reads:
CHECK-IN TIME for the Vacation Home is 4:00pm.
CHECK-OUT TIME is 11:00am.
"anytime after" is not included in the wording on the confirmation.
I agree 5:30 is too late, someone should have checked into why it was not ready before then. If the reason was housekeeping didn't have it marked as done, someone should have checked and it could have been easily taken care of. One time we were checking into the Beach Club and our room was not ready at 4:00pm, the front desk cm personally went to the room to check it, they hadn't even started it (our assigned room was on the second floor, not far from the lobby up the steps)! So she found us another room.