That's a common comment but actually isn't true. Some great movies have fantastic Peetimes. Take for instance Captain America: Winter Soldier. (Lets not debate how good the movie was. I think it was at the very least a well told story.)
At any rate it has a fantastic Peetime. There's an entire 4+ minute span of Steve and Natasha entering the old Army base where Shield began. There's almost no dialog, it's just them searching as the tension builds. As a story telling device it's an important scene - building the tension. But if you need to take care of some urgent biological needs this makes a perfect time to run and pee. :-)
I think you missed his point. He said "relative" amount of Peetime. Meaning if a 2-hour movie has 1 hour of Peetime, you may want to pass on that movie altogether.
