No, I assure you, he wasn't talking about those girls and Eric lol. It's not that they won't do shit with other guys, it's just not NTR. They're not in a relationship with Eric, nor is it malicious, therefore it's not NTR. When I say I'm friends with the dev team, I mean like, I'm very, very close with most of the dev team, I'm not basing this on conjecture. NTR is about cuckoldry. Eric isn't being cucked by them because he'll still be fucking them himself, he's not being cheated on because he's not in a relationship with them, and he's not being betrayed by them because there's no expectation for exclusivity and they still care about him. I mean if your definition of NTR is so loose as "anyone who is remotely related to me does sexual things with other people without neccessarily telling me about it" then sure, I guess those relationships are NTR, but that's an absurd definition.
And the game is Shadows of Ambition

I've helped Abyss since chapter 2.
Also don't read too much into a single world like "relationships", english is not CG's first language nor is he so specific with his language. Like I said I've talked at length to CG, but more so his team about the game, I'm not basing what I say on conjecture or random off lines by CG.