I have big dogs. I never allow them off-leash anywhere where it is not allowed.
I have a 60# Australian cattledog that has gone camping with us in Grand Teton NP and visited Yellowstone NP. She has to have her ball-chasing time so that is off-leash. However, I always managed to find a place well away from other dogs and people for the exercise time so as not to give cause for notifying authorities about this rules violation. In camp and at various sites (i.e. Old Faithful), we held to the NPS rules as regards the leash.
Given the SanFran location, I’d say the rangers there are a little more strict and unyielding.