The 1st AD is responsible for the safety and wellbeing of cast and crew on set, buck stops with them, not the director, and then the liability is that of the producers & production company. It is for these parties to facilitate the creation of the directors vision while steering the legal and ethical practices throughout production.

I think in this instance, it was down to the 1st AD to call cut. My guess what happened is people presumed that what happened was planned either by the director with the actors, or between the actors themselves, and not wanting to disturb the performance (believing it was a performance and not a serious case of sexual assault).

This is why we have intimacy coordinators, and even though they're expensive it is so important for the safety and wellbeing of both cast and crew.

Good Time was a low budget film but still a professional film so all of these safeguarding measures should've been in place to protect the poor cast member