As shown in my AIM-54 analysis videos, it goes active at about 7.5-10nm away from the target. As far as I understand it, in the real jet, the RIO can choose when it goes active, but in DCS the game engine does it, and as far as i know HB does not have control over this.
As far as content creators go, speaking for myself, I try to be as accurate as possible, but hey... sometimes things get fouled up. Good content creators will acknowledge these issues and either correct them or make sure to double check related facts next time. Shit happens, move along ;)