To be fair is kinda like chick flicks and actions movies: A majority of them follow a format. Girl who has a crush on guy, guy who has a crush or is bf of the queen bitch, best male friend who has been in love with the female protagonist since they were kids, you name it. This 2 games just happen to have a MC who is a superstar, so it's normal they gonna have similarities (just like any normal sport movies as well).
Even in this platform, it's very common to have the 'Young goodlooking MC with an impressive cock whose father died/disappeared, and he lives with his m-...landlady and sis-...eh, roomate! (man, if I had a nickel for every VN that starts that way...).
I followed the other game with the faceless MC and duckfaced girls since it released. I've also been following this one, that's why I can see why you say you find certain similarities (again, because of the superstar format), but I also can see why they're so different. Tone, pace, girls, dialogues, looks. If some scenes are similar is, again, cause they aren't only following the sports format, but also the AVN/seducing game format.
There are so many books that start with a young hero who is or just became an orphan (Harry Potter, Eragon, Name of the Wind just to name a few), yet I wouldn't call them the 'copy of a homework in a way no one can tell it's a copy'. Eventually they all leave the initial format and become their own thing.