a trap is a male who dresses up as a girl. its not offensive.
It is offensive, as it is often used as a slur towards trans people
There's lots of people that embrace the term/idea as a kink, so that's why it's there. If it helps, I don't intend to write traps in a negative light.
To further clarify, that kink in this game specifically refers to a male that the player expects to be female, then finds out is not. I fully expect anyone offended by such content to just disable the kink, in which case it will not appear in the game at all for you.