If I went to the hospital and a nurse gave me any instructions I would be absolutely perplexed.
I'd assume that is what OP is talking about at least. It's getting rarer to see an actual physician for most visits in many areas.
Edit: thinking about it more, I've received referrals directly from nurses before as well. Usually the triage nurse.
If I went to the hospital and a nurse gave me any instructions I would be absolutely perplexed.