No it's a "refresher" for AP students because the AP test actually TESTS that period of time.
Look, this is a niggling little point that I don't want to argue over but the piece (which is not very strong on facts but alludes to them obliquely) clearly talks about the "refresher" as separate from the AP classes.
"...other than a little optional "refresher" at the beginning of the school year or if you're in an Advanced Placement class.
"Or" is the operative word in that sentence.