Almost every IB class at her school is designed to also cover the AP tests. HL English is broken in to two years of AP lang/AP lit. HL History of the Americas is broken in to first year APUSH second year, everything else. HL Chem student all take the AP test too, SL Econ kids take the AP tests. HL Spanish is AP Spanish Lang first year, Spanish Lit second year. And so on.
I suppose it helps kids going on to colleges that don’t give credit for as many IB classes as they do AP.