Just like PPs have said, it solely depends on occupancy and will vary every time. Even if 100 people got in their room by 8am, it doesn't change the odds for the 101st person.
FWIW, we've never gotten access to our room during our stays at RPR and HRH before 1-2pm. I believe one time, it was closer to 4pm. And we generally travel at slower times of year. I do think Universal's housekeeping is better than that at WDW, with more care and attention given to each room, thus taking the process longer. Just my personal observation.
Like PP mentioned, you can check in and they will give you faux keys to use for EP if you want to head over to the park. You will have to stop back again at the front desk later to have your keys re-keyed for your room, obtain your room number, and have your key activated for charging privileges. I think they are supposed to send a text, but I only received it one time and have had to stop back at the front desk every time.
Another option is to change your reservation to check-in the night before, so you'd definitely have a room ready when you arrive. Of course, that means paying for an extra night. If you go this route, call and make sure your arrival time is noted on your reservation so you aren't processed as a "no show".