Yes , this is why it is much better if the dog decides that you are a better leader, rather than try to force the fact that you are Alpha onto the dog. If you can get the dog to choose you as the leader you are already winning. Insisting, calmly and quietly, that a sit is what you asked for and nothing else is good enough reinforces standards and authourity - how many people would let it go when the dog lay down? He is staying in one place and is quiet, so what's the problem?
I'm so happy you have found a behaviourist that you can work with so well.