Given A) how difficult it is to get into medical school, and B) how critical your MCAT score is to getting in, and C) the material covered in AP Bio, AP Chem and AP Physics 1 & 2 is all test in depth on the MCAT, I would be nervous if DS was planning to use the AP credit and was not taking the courses as a college freshman (sophomore in his case for physics).
FWIW DS got 5s on AP Bio and AP Chem and a 3 on Physics 1 (Physics 2 not offered at his HS). AP Bio doesn’t count at his school for either of the first year biology classes for majors anyway (credit only given for gen ed biology for nonmajors), so that wasn’t really an option anyway.
I like that he is repeating all for MCAT review purposes. I love the idea of using AP credit for gen ed credits (social sciences, English, A&H, etc.) where you aren’t planning to take additional coursework in the subject. But not for these critical science classes that are on the MCAT, material you want to have down cold.
Even if you have a lot of AP or DE credits when you start undergrad, trying to graduate in three years and start med school in year four seems like a really hard thing to do. Your taking the MCAT and applying to med schools in the spring and summer at the end of your second year of college, so you are losing a lot of opportunity to round out your resume.