I had a PT tell me something similar. I didn't hurt my shoulder doing TA, but a workout with endless reps and light weights. He had me do a stretch to check my range of motion. He told me my arm wasn't supposed to go that far and to never do that stretch again.
This was years ago and I am no longer so flexible in the shoulders. I still avoid fast and or high rep workouts. I really pay attention to my form when doing shoulder exercises.