Shoulder impengment and PTs theory.

I have read the blue book on shoulder impengment and what it is. My question is, the PTs like to say pec tightness and upper back weakness causes it. Would this be true or false? I feel if you have a normal bench to press ratio all parts of the roator cuff are strong. Also say you bench 300 and deadlift 500 how is that a weak upper back. I figured impengment was manly because of a growth under the ac joint that aggervates the soft tissue bellow. Or it was inflamation due to say a injurie that causes less room in the subacormal space. Is this pec tightness upperback weakness more PT fruad.

Your spelling is terrible, but your reasoning is solid.