green flag or red flag

I honestly don't care if a story have green red or black flag but I'm just confused on how ppl judge a story. I was reading The Story of Monster and Asuka and obv I want more of the monster x human dynamic so I look up the list to see if someone has already made a monsterfucker list.

but why do ppl put this story on green flag/healthy relationship list? and unproblematic? have we lost the plot??
the seme is a monster. besides the size difference (that could be harmful to he human), the monster regularly broke in to his house and invade his privacy. he also made pervy remarks all the time, tho the mc is fine with it. and this is put on the GREENEST of green flag.
I understand since he's a monster he is the greenest flag but this relationship is far from the greenest and unproblematic.
I can't trust others list ig