Lots of nurses get consent forms signed for open heart surgery and other procedures.
I have heard it argued, "Just ask the patient if the doctor has explained everything to them and then get their signature. You are only witnessing that it's their signature."
That is a legal nightmare. Patients are frequently under the influence of many mind-altering drugs. They often report later that they can't remember anything anyone told them. If I wasn't present when the doctor talked to the patient, how can I say that the patient understands? I was at home in bed!
I'm supposed to ask a drugged, very sick person to sign that they are okay to have a complicated surgery (which I probably don't understand) and then put my name by that? A lawyer would destroy me in court.
If I had been to school as long as the average surgeon, I think I might be able to remember to take a consent form in the room with me when I talked to the patient.