Bolt thrust or back thrust; I don't care which applies (and I'm normally very sticky about nomenclature).
It is a fact that a properly functioning cartridge in a properly made firearm expands upon firing, and it as least partially held in place by the surface tension that is induced by the interface between the brass and steel surface under pressure. Even with steel cased ammo, you rarely see gas intrusion as far back as the cartridge body, because chamber pressure seals that.
What is your version of why H&K uses fluted chambers? Care to provide a link?
The guy who cleans brass after sizing and before priming, charging and seating bullets has a very good procedure.
Tumbling after loading must be OK, because that's what the factories do.
You say that this isn't a problem with .45 ACP. I doubt that you've fired any .45 ACP that developed chamber pressures in excess of 50,000 psi.
It makes zero difference to me if the peanut gallery thinks I'm wrong. Go ahead and leave the lube on your rifle brass, and be sure to carry a few extra eyeballs in your spares kit.
And Rocco- There is nothing more important than keeping your body parts intact while shooting.
Nothing; nothing, nothing.