Working Dogs Crossover to Companions

"Pressure" in my way of thinking, is exactly what "P" would mean in an operant sense - something that would tend to inhibit the dog's behavior

 
It sounds more like your providing boundaries or guidelines, wherein the "pressure" is to perform in a certain way or direction. And some working dogs are self-rewarded, I think, by the work, such as my BIL's Blue Merle Aussie. Nothing pleases here like going after the "sheep" conveniently shaped like a ball. In fact, my nephew was running her ragged until SIL told him to stop. She need to lay down and cool off. They have a water garden in the backyard that she loves. Anyway, even when tired, she would go after the ball, again.
 
And you are the only person I know of here who has scruffed harder than I ever did. But it sounds more like your dogs are eventually training themselves with the boundaries and "pressure" you give, rather than standard obedience. Also, the herding dog doing what he/she loves has a training regime that is self-rewarding.
I could be wrong on that. I've been wrong before and I'll be wrong again. Juxtapose that to obedience training, where the dog wants to jump and love on someone, which is self-rewarding and I want mine to do the opposite of that, which means making off or sit more rewarding than the jumping, at least for me.
 

I use "pressure" to direct a dog around an agility course-- note I said "DIRECT". It's just information. I can flip an arm and send the dog flying away, step sideways and push him sideways, have him drop on the table, none of this "punishment" : it's information.
If I'm "fake hunting" my cross bred bird dog I use "pressure" to change her direction in quartering, may ask her to "drop" if she's "pushing too hard" on the birds I can see and they'll flush too soon (pretending I want to shoot them). It's not punishment, it's DIRECTION. You're simply providing information about where you want your dog to be and what you want your dog to do. If your dog scattered the sheep and you harshly downed the dog and scruffed it to remind it not to do that again, that's punishment.