Reona is no exception. She should have her NTR scene changed to optional. She's an Li so it's still in the realm of NTR. Netorare Is essentially about someone else "taking" from you. Whether it's one-sided, unrequited, platonic, or whatever. There doesn't have to be a sexual or romantic relationship for it to count as Netorare. Netorare isn't just cucking it's a bit more nuanced.
It has to do with the fact she's an Li so it's inevitable that we'll be together and during the time frame of the game I wouldn't want Li's fucking other characters, at least without the players say so. This is only my thought process for a game though, in real life I wouldn't think that way. That's just unreasonable.
If she already had sex in the past before the game, that's fine, but I don't wanna see it while I'm playing, are my thoughts on it.