End of the day I think it's derivative to call the game a power fantasy just because it focuses on the MC getting girls rather than side characters, especially since it does acknowledge several of the dudes sleeping with girls that the MC can also sleep with. There's lots of other aspects of the game that are very un-power-fantasy so I think labeling it as such due to one aspect is missing the forest for the trees.
It's also a power fantasy for plenty of other reasons, just not because every other male fails to maintain their relationship and MC is conveniently available and accessible to swoop in. If its done once or twice I would've shrug it off, but its a common fake obstacle that only pretends that MC has to fight the odds, when practically its playing right into his hand. The new crush has a partner, damn. But their turn out to be lesbians, so they are more likely to share or break up. The hot girl has a boyfriend... but he turns out to be gay. The other hot girl has a partner...except its one-sided. The nerdy girl loves the nerd... but the nerd ignores her and she is frustrated. All these girls are frustrated with their current partners, how convenient that MC can swoop in!
Moving on, we may clear up the definition of power fantasy, considering the game is very clearly one at least in my book. Introducing MC as a slight loser, underdog, issues with getting girls, money, qualifications, family stability, but very rapidly on his way to become successful in all these aspects and getting endless opportunities, without being particular above average in anything? How is his personality and presence noticeable better than Derrick or the third guy that lost the fraternity qualifications? At first he is scoffed of and belittled by everyone, but at the same time gets a second digit body count in a span of months, can't really fail, most conflicts are merely seemingly ones and end up being a springboard to greater highs.
"Normal" stories have an MC form a relationship with one partner over the course of the plot, usually by devoting themselves to it, which is fairly realistic. Not being a gigachad sleeping through his entire college.
Finally, I don't mean power fantasy as a derogatory. Many porn games are one by design and work as intended. So it isn't even a criticism of the game, mostly just an observation when I compared it to another game.