Powerbottoms are the same as dom bottoms/bottoms. Never did I once assert that he wasn’t a power bottom. Also the implications of saying “despite not being the one putting it in, he’s still the top and the dom” allude towards a conflation between two different terms. Power bottoms are bottoms. It doesn’t matter if he’s riding him, he’s still not a top. Educate yourself about the BDSM community please.
Your logic is like - "why would the term sadistic domme exist in the first place if domme already exists?" A power bottom is a BOTTOM that likes to take control. They are a bottom that takes control, and power is a descriptive word, just like sadistic or gentle dommes have a descriptive word before domme as an indicator of their preferred dynamic. Learn grammar.

omg the top is scary but i like it