Musing about this this morning. Math and CS would definitely require a strong foundation. They almost totally build upon themselves which is why (IMO) a student who struggles in Alg 1 shouldn’t be pushed on to Geometry and Alg 2 even though that happens all the time. Chem and Physics mostly build upon themselves too, more Physics than Chem, but that’s probably due to the math involved. Still, with each of these there are a few topics that could be missed and one could still do well elsewhere in the subject. I could see some getting by in Bio with gaps as long as they had the general basics that are covered in pretty much any course.
That said, it seems common that at “usual” transfer schools, the deeper material is often covered in later courses (as with that DE Prof), so students don’t really miss out. It’s just a different focus on whether that material is needed early in a major’s student life or later. Then too, when in earlier classes, ALL students taking that course get the material. When in later courses only those taking the higher level courses get it. That’s one of the big reasons I only recommend higher level schools to students who really enjoy academics and have the ability to do it.
Want to be a doctor? Any school will work if you do well. If you don’t care for the deeper level classes, stick with an easier school. If you love academics and study, the easier schools don’t have as much to offer.
I KNOW there are posters on here who claim that ALL pre-med courses are the same at any school. IME with oodles of students, that’s just not true. But it’s also not true that one needs the higher level schools (or their courses) to get accepted into med school. A top student can get bored at a lower level school (my middle son’s peer had this happen, but he’s still going to med school). A good, but not “loving it” student can get needlessly overwhelmed at a school where it’s too deep.
Select the school to fit the student. It’s not one size fits all. The CC route works well for many students, but not many transfer to super top schools for obvious reasons. (Some do - there are probably some who could self study and still do well as they have that much mental ability and initiative. Most don’t. Plus CA may be a totally different creature with their levels covered in CC. Without seeing them or students who take those classes, I have no idea.)