It's not a good idea to Ctrl+C the entire essay from your primary for any secondary, even if they don't out flat tell you not to recycle your primary essays. But you don't have to come up with a entirely different essay either. Take your primary essays, rephrase it a bit, tweak it here and there, maybe use a different opening/closing paragraph, but recycle the more technical part (structure/data presentation/discussion, etc.). Shouldn't be too hard to do. As for the non-technical (i.e., bulls***ting) essays, I would write a new one, approaching the same story in your primary why MD/PhD essay, but from a different angle. Some other schools ask similar questions on their secondary (plans for MD/PhD, role model, to name a few), and you are more than welcome to Ctrl+C from/to those, and UCSF won't know😀
PS: Jana and Catherine don't return every call/email, unless it's urgent or cannot be resolved without their intervention. General questions like "with these stats do I have a shot" or "how should I go about writing my secondary" don't have definitive, fool-proof answers, and the directors' approach may not be the same as the committee's.
PPS: Might be another good topic to add to the stickies. With our highly redundant MD/PhD secondaries a lot applicants each year will wonder about the same question.