I've never seen a physician office that wants patients to be there right at the appointment time. There's usually a request to get there a bit early for checking in and demographic/payment updates. Your appointment is with the physician at 830, not the front door. If I were your physician I'd expect you to handle all the other shit a bit early or just have it eat into your time. Wouldn't matter to me in that context. This probably why physicians always seem to run behind 5 or 10 minutes. Conveniently the amount of time they usually request you to arrive before the appointment. I can imagine lots of people do what you do.

I don't really care what you do. Just don't expect me to buy that you're always perfectly on time.