You are correct in much of what you say, but the reason that safe words are so important to a Professional Domme is simply because she doesn't really know her clients. She hasn't spend hours to days discussing things, leaning things, and communicating with him. She has him for a couple of hours usually, and needs a way to know that something is wrong. In addition it is the client's fantasy, not hers. He is paying her to make a fantasy reality.
The lifestyle Domme experience is different. I don't use safe words, but if a male said "Mistress, my heart!" or showed signs of a medical emergency, then I would act accordingly. The point is I encourage honest communication. It's an actual relationship where I get to know my sub.
