LI = love interest. A LI is basically a girl the mc can romance, and as you pointed Flavia has sex with someone else , that is netorare content. You should warn people about the content your game have. Also, if it was true you don't understand what ntr means then why lie and say "no ntr scenes"? (even more when the game actually has such content.)
I think yea from my part i think i was wrong i replayed it and yea the dialogue it hints that way but i think is not ntr ,this guy is just talking nonsense don't listen to him .
What models do you use for this ?
Make the story and game the way you intended too.
Just small warning if u use patreon they don't allow incest so they can delete your account without warning use subscribestar better it takes longer to be approved,but is better regarding that kind of content or change the dialogue.
All in all the game is not bad is different so keep it up and again gl .