It's not the dev who's "problem" here, but folks who expect entire world to fit into their personal definitions of certain tags.
Take for example some popular games, as BADIK. Numerous side girls banging other dudes, numerous side girls making their living of the prostitution etc. Game is not NTR tagged. So why this one should be? For same content (random MC unrelated girl banging some dude) but on much smaller scale?
As for harem, definition nowhere states that it MUST include ALL girls in the game. If, from 10 girls you can "haremise" 5, that's still harem. It also doesn't state that all of them must be immaculate virgins.
So there is no NTR and there is (will be) harem.