I think it was only EricaP who read the letter as being from a woman -- not "everyone. We also do not know whether the doms might already be faking leaving. It is that I would never take on the responsibility of actually leaving as a dom. I was assuming LW was a man, because of the line you cited. There are ways to fiddle this for safety, and people can and do do that, just the same as "rape", "torture", or any other thing that would be a Very Bad Thing in real life.
It is that I would never take on the responsibility of actually leaving as a dom.
In other words, the BF is behaving emotionally questionably but not ethically questionably. I think there are still too many unknowable issues to consider this wise. Now, in a cursory glance around Google, it's difficult to find non- law enforcement sources discussing the safety of this technique. If their partner is not home by a certain hour, some prescribed action could take place. Would people not accept a similar quantifiable risk for other leisure time activities? And the LW has no way to know if that safer version is what actually happened.