In my absolute hypothetical a couple of things
-The first semester transcript would show the AP Calc class, as the student switched in January.
-I do think that recruited athletes are probably more in the loop than your average student on protocol. I wouldn’t assume any 17-year-old has the common sense that if he switches a class, he needs to let a college know. It is certainly second nature to parents on CC but not to high schoolers. I also think kids who are athletes and going through the hoops of selective D3 admissions have parents who are more involved and knowledgable but I bet 99% of the parents at our school wouldn’t have a clue.