The question I have is if he's cutting your time short. Like, you end at 10 til, but start five after. That's 45 minutes and sure, I'd say something.

On the other hand, for example, my T works in a clinic. Every single T grabs their client five after (I've noticed how the door opens between the 5-10 minute after mark and the waiting room ends up with fewer and fewer people). I've never been shorted time and I recognize this is the way the clinic runs it. My guess is my T works back to back clients and so this is a few minutes to prep for me.

Since he works in a clinic his start time is whatever time he gets in. So, even if I were his first appointment, I wouldn't expect him to get me until 5-10 minutes after the hour.

Also, the clock thing. Most places I've ever had appointments with allow for at least a 5 minute discrepancy. So maybe you think he's 5 minutes late and he thinks he's only like 2 or not even late at all.