Which IMO has zero correlation with course and/or test difficulty. Chinese and Japanese scores are skewed by heritage speakers and Calc BC and Physics C scores are skewed by the fact that the students are self-selecting these courses and are often the very high-performing STEM kids.
On the flip side, the high percentage of ones can possibly be attributed to the fact that some students are jumping on the AP bandwagon that should perhaps not be taking an AP class (or as many AP classes). APHG, where offered, is often a freshman/soph honors alternative. AP Physics 1 is partially the result that many schools eliminated honors physics.