I think you could be right. I know exactly what you mean about GSPs getting over excited and I would imagine you would tense up in expectation of this and he's picked up on this. Is he the same with different handlers?
I knew someone with a little dog that used to chase horses/joggers/cyclists etc, she would always shout and panic and it made the dog worse, so she tried ignoring it and eventually the dog got the idea and stopped.