Condescending? Rich coming from you Super Chief. I have never asked what a pull time is even once. The departure time is when I depart after determining equipment and cargo that I am responsible for is to my satisfaction. There isn't a person in management, any UPS regulation, etc etc that can dictate otherwise.
You are asking about legality and such. Securement is like every other regulation in the book, it's at the discretion, interpretation and mood of the LEO you are dealing with. A half loaded trailer that is floor loaded with no Securement? You'd have to be acting a complete fool to the officer or he'd have to be having a really bad day to cite you. DOT guys aren't that bad to deal with. Like any law enforcement, 99 percent of how they deal with you is how you deal with them. Now if you are talking about a load to the doors and stuff comes flying out if requested to open, that's probably going to go a different way.
Evidently our hub is different than some. At the trailer cleaning doors you can always find straps, nets, bars and usually even butterfly bars.