In the case of some of the DB'ers, they went ahead and filed themselves and when they took action, it snapped the WAS out of the fog. If you feel your S has overstepped your boundary more than you can tolerate, then you'll figure out if you want to file or not.
or the opposite could happen .. the WAS can walk away with less guilt because the WAS didn't pull the trigger and file. having the LBS take action could be something that the WAS is hoping for so that in the end, the WAS could say "you also agreed that our m was over. you didn't fight for us because you ended up filing, not me".
i don't know if that makes sense .. if not, pls ignore.