Honestly, I am not surprised the boys at Patreon missed it, even if they inspected the game 5 times.
I've done many playthroughs myself and hadn't noticed until I got that warning on Reddit and looked into why. And even then I was still scratching my head in confusion... lol
If I had to guess, I'd say this could be because the character age in question is a male and the MC, and not the expected underage girl they usually look for and find in the games they ban.
But who's to say that one day they won't wise up to this and decide to ban the game? Nyx is smart, she may seem like she is doing it just to appease the players bugging her about it, but I am sure she also knows that she is on thin ice with Patreon too, especially with the recent changes. All it takes is one savvy inspector and it all goes up in flames.
A Patreon ban will be a hit right on the money. It will hurt, and that's not worth the risk to the project.
Either way, I think fixing this, no matter what her "real" reasons are, is the right thing to do for herself and the game.