Has anyone actually had luck with the 'nothing in life is free' training method for a stubborn lab?

My 18 month old lab Tucker is... a lot. He's not aggressive or mean at all, he's just completely convinced that the rules don't apply to him. Sits when there's a treat in my hand. Otherwise? Good luck. Trainer suggested we try the nothing in life is free approach where he has to earn everything.

We're on week two and honestly i cant tell if it's working or if Tucker just genuinely doesnt care about consequences. He'll do a sit before meals, that's going well. But asking for a sit before going outside? He just stares at me like im speaking another language and then looks at the door.

He's not dumb, labs definitely aren't dumb, he's just... motivated entirely by his own agenda. Has anyone gone through this with a lab or really any high drive dog? Does the NILIF method eventually click or is there a better approach for the "i do what i want" personality type? Would love some real world experience here because the internet gives very optimistic answers lol.