I don't know if that last part holds absolutely (the first part neither, but that's later)
Someone's preference on the topic of penetration (receiving vs giving, top vs bottom) can be completely separate from someone's preference when it comes to power dynamic (power bottom vs pillow princess) can be seperate from someone's preference in specific bdsm power dynamic (dom vs sub)
A "power bottom" is not inherently the same as a dom (at least it didnt used to be; in current days, a lot of queer terminology has been "taken over" by hetereosexual sexual acts, and have changed meaning as a result). A power bottom can also be seen as someone who is the more "eager" or "active participant" during sex (e.g. they give the ideas, they spur the other on to do something a certain way, such as "harder!" / "faster!"). It has sort of more to do with "level of enthusiasm expressed" than a strict power dynamic. Same as a pillow princes: they like to lay there and be pleasured, but that does not mean they inherently also like being dominated.
A dom is someone who is dominating the other. Its a very specific kind of sexual dynamic that is seperate from if someone is a power bottom or not. Someone can be a power bottom but still want to be dominated by the other via constraints, whips, whatever else they might prefer.
I think it's the difference between being dominant during sex (verbally, by way of sounds or acts) and actually dominating someone (a different dynamic which requires different acts and different power rules). A power bottom is dominant, but does not inherently dominate the other person.
I do wonder why a woman pegging a man is more empowering than, say, a female dom tying the male down and riding him "just for her own pleasure" (in a bdsm-game-sense, consensually). In that way the sexual act is (in the bdsm-game-sense) focused on her desire and pleasure, while the man (consensually) lets his body be used with the main goal of pleasuring her, and not himself. This is a scenario wherein the woman is not penetrating the man, but is still the one having power.
Dominating =/= being the penetrating person during sex. In your first comment you equate pegging to domination, but thats just... not universally true. You have oral sex, you have lesbian sex which does not use penetration but can still have a dom/sub dynamic.
By keeping the idea of "penetration = masculine = power" alive, you are not being feminist. The whole idea of the phallus being the signifier of power, and the female vulva being the signified is tied to this. As long as penetration = phallus = power stays alive, the idea that the masculine act in sex equals power, equals power in the general sense, stays alive. That is not feminist.
Turning the phallus = masculine = power on its head by having a woman be the one penetrating ("using the phallus") does not change the order of things. You are then still working in and existing in a framework where power and domination is tied to men.
Feminist praxis should not be "using the masculine framework of power BUT done by women", it should be "changing and erasing the purely masculine framework of power".
(The first framework is what you see in movies too, btw. When a female character is strong and powerful and to be taken seriously, she is always acting or presented as "like the men" due to clothes, way of talking or acting. This all still keeps the notion of masculine = power intact and is NOT feminism.)