Agreed-- and the level of instruction is different.
Although I will also say that college courses vary ENORMOUSLY in terms of how much work is graded/submitted. Many STEM classes do still have graded homework or lab work associated.
Every class I ever taught had at least 20 graded assignments in it. At least. Some had as many as 100 over the course of a 16 week semester.
I didn't know anyone that had fewer than five, and most of those people had some kind of safety net for a student that missed one of those (or just plain tanked on the day, iykwim).
I'd also say that it really depends on the AP course. My DD's AP courses have all had far, far LESS instructional scaffolding than she will expect from college coursework. In fact, the expectations and requirements are quite similar. She has teachers that she hasn't even exchanged a sentence with all semester. Her AP Stats teacher, for example, never has class (he just doesn't), refers students to youTube and Khan, and communicates 99% via e-mail in one-sentence statements. It's the equivalent of being a student in an 8 am class with 200 people in it.