" can only quote the French mountaineer Gaston Rebuffat -"You will never regret beginning too early, you will always regret leaving too late" "

A lot of truth in those words.
I can remember so many times when I was in the mountains, I was up at 4am. sometimes 3am. make some quick coffee, eat a snack, check gear and GO!! Moving in the darkness - before sunrise.

You have a good point. They needed to be finished with Keyhole Canyon by noon. Afternoon is the worst time to be in those canyons - in AZ Monsoon season.