Nyeah... partly.

If that were entirely true, a "power bottom" would make no sense.

The terms sexual usage originated in gay circles where it only delineates who penetrates and who gets penetrated. Traditional views on sex ascribe a submissive or passive role to the bottom and an active or dominating role to the top, but you can totally have a power bottom who takes control and an active role in the intercourse but is the one getting penetrated.