Most physicals I've had, I'm told to strip down to my underwear, and it's usually the nurse that tells me as such.
In a recent appointment, it was by my doctor, and about 5 minutes-ish into the exam. She just needed enough time to get acclimated to the environment, and what she needed to do for my treatment before asking me to change. I was told, "to prepare" for my next protocol (in this case, injections). I stripped to my underwear, which for the time being, are cotton panties. She didn't really tell me how much to strip down to but, due to where she was working, i figured it was best to steip to my panties. I waited at least 5 to 10 minutes. Probably in between, around 7 minutes. Sitting on the table, in my gown that opens in the back. I also kept my socks on because the room I was in was cold.
In this case, all she did was reveal my backside as I needed injections in my neck, back of head, and all across my upper back. Occasionally, she'll give me injections in my lower back, so that's why I stripped to my panties, just in case. Every appointment with her, is a little different each time.