My pediatrician days were mostly in the 1970s and early 80s, so undressing was not as big of a deal as it seems to be now. We went to a number of different doctors at different times but a physical always meant wearing no more than underpants and, for a couple of doctors, being fully naked.
I remember a clinic we had gone to a couple of times when we were sick and my brothers and I only had to pull up or, sometimes, take off our shirts. But we went to that same doctor for a physical and the doctor met us while a male assistant/nurse was leading me and my brothers and parents into an exam room and as we went in and the nurse was setting up the room the doctor said to my parents "everyone feeling ok today? The boys are here for physicals? Ok... we'll get them ready and I'll be right in."
The nurse made a little small talk about school and sports and I remember him checking the big light over the exam table and he said to my parents, "have the boys get undressed for me. They can leave their underpants on for right now but when the doctor comes in they'll have to take those off, too."