In our experience...
Early evening seatings tend to be more likely to seat on time. Later seatings run more of a risk of getting caught up in the backlog as the evening goes on.
We had 7 PM ADRs for Le Cellier once during the Food & Wine Fest, and waited more than an hour (closer to 1.5 hours) past our ADR time to be seated in a very crowded and noisy restaurant. Add to that the fact that we did check in 15 minutes prior to our ADR, as is recommended. Waitress was totally frazzled and burned out by the time she got to our table that night, so was very 'short' with us and did not check back to refill drinks, etc.. Not a fun dining experience to say the least--although the food itself was admittedly quite good.
Any ways, how promptly you might be seated will depend on the timing of your ADR, combined with how busy the park--and more specifically the individual restaurant--are that evening.