Is premed friend doing the right thing?

So I have a friend that had pretty good stats (GPA 3.9, MCAT 36) and attends a HYPSM school, but ended up getting into a mid-tier med school that he wasn't happy with. He said that he wants to be more academically inclined, but not take the MD/PhD route. As such, if he were to attend a mid-tier med school, there wouldn't be as many or any opportunities for being an outstanding applicant for residency. So he deferred enrollment to his current med school acceptance so that he could apply again in this cycle and potentially get into a better school.

I want to say this is against AMCAS rules somehow, but I'm not sure. I'd like to advise against it, since I feel like it's something the medical school will see and potentially rescind the acceptance for. On top of that, being a reapplicant while previously holding a med school acceptance it's considered a death sentence for admission... What can I say to try and convince him that doing this is a really bad idea?