I thought I saw this already and someone had answered what I think is the correct answer (maybe another recent thread?). The OP says this is their first rental with National. In general, national does require you to go to the counter for that first rental, I would *not* count on just picking up a car and going to the gate.

Now, expired/new drivers license does tend to trigger the message about going to the counter, and for that, in general it's something that can be taken care of at the gate without a problem.

But if it's your first rental? Expect to go to the counter. I don't know SFO's setup, but you might be walking past it anyways on your way to the cars, and as noted, often the national counter can be pretty empty.