So due to this FAQ a qinggong monk which has replaced abundant step (or another monk ability) due to an archetype can't retake it as a ki power.
But can a chained monk with the Student of Perfection prestige class (outside of PFS of course) choose a monk ability they replaced with an archetype as a ki power?
Yes. Quite frankly, the reasoning given in the FAQ is super flimsy, and if it would apply to Student of Perfection, no one could select any of those ki powers.