At least for Computer Science A, BC Calculus, Physics C and US History, the tests are nowhere near college level. Plenty of people get 5's on Calculus BC and can't tell you how to derive, say, integration by parts. Or how the Mean Value Theorem works. Or really anything beyond regurgitated power rules, etc. And Physics C? I got a 5 on both tests with some pretty terrible answers. The courses, sure, depending on your school they can be really great and beyond college level. But they'd still be great and beyond college level if they were just regular advanced classes.

Not to mention some AP tests are rather ridiculous. Like AP World, which is a test on all of history. Could you imagine a test on all of math? Plus it doesn't count for anything. AP US History doesn't get me out of any classes. It didn't add anything to my application other than another number. And I didn't really learn much either.