You have so many hypotheticals that’s almost impossible to answer your question.
Med school admission is so idiosyncratic. He may improve his standing with some adcomms but not with others. Adcomms aren’t a universal block. They are a group of individuals who volunteer their time as a service to their institution. It’s impossible to say with authority or certainty how any particular individual will view X, Y or Z or whether their opinions will hold sway with the rest of the committee. My gut feeling–and this is just my gut feeling and not an informed opinion-- is unless your son is applying for a MD/PhD program, the response will be “that’s nice, but let’s talk about those ECs…”
My advice would be the same as @ucbalumnus above–he should concentrate on fulfilling this admission requirements for the program he’s already in and take the coursework you’ve mentioned ONLY if it somehow mets a need or interest that is his own.