My nephew and I walked in to Teppanyaki with no PS at about 8:15 and were seated immediately (well, actually, we were seated as soon as the maitre'd found us some towels to dry off with...it was pouring and we were soaked). It took about an hour to eat, so if you're seated at your PS time you should be okay.
The only question I have is: we were the last two seated at our table, and all the others had already ordered and were waiting. The chef didn't come out until after we had placed our order. Would the other party have had to wait longer if it had taken them longer to fill the seats?