This is something I understand from reading the LN. But god's are very active. Tittles, and certain skills are given by the gods, be it by acknowledging or directly imbued.
Fran, someone experienced with torturing, has not been given the title of torturer.
Fran and sword always, wait to attack for the most part. Or rather the sword. As Fran is pretty blood thirsty.
Secondly both of them can sense malice/ evil intent. So it's very rare for them to move out of line.
@Duck_ - he was lucky he was tortured by Master who has that truth-detecting skill. Most people would have kept torturing him a lot, trying to extract information the assassin doesn't have. I guess it's better to die quickly. Especially if punishment for assassins is death anyway.