If you came in with several accepted AP credits, took summer school, and loaded up on classes each semester, you could theoretically finish in 2.5 years. However the reality is that some classes cant be taken concurrently, some will not be offered when you’d need them, etc. However you could finish in 3. My wife did this. But it was because she was bright and enjoyed school. Most people don’t take summer school courses, especially premeds who want to do research gigs at the NIH, etc.
My nephew is also a Mensa kind of guy who was taking college courses starting freshman year of high school as part of some gifted program. He took the full 4 years to graduate. He took more classes than he needed, did a double major, semester abroad, travel programs, etc. He did that because college is the time to explore your options, spread your wings, live a little. There’s no reason to blast through locked in your dorm room.
Life is an adventure.