I agree with your whole post but that one line.
I see two levels/degrees within submissive .
Submissive
Slave as stated above ...... much less less options and input ... Things are usually clearly defined in consenting relationships before hand and as the two get to know each other.
( some ( -- nc) think it's all about Whatever is said by the Dominant one. I have wondered if there should even be levels within being slave or not. -- I question this type of slave relationship as unhealthy in my view point. )
Pet .. known for playfulness, given more range of freedom and input .. just as you can't always control cat - kinda very much in common here. I don't expect that kind of control from a pet. If you walk away from a cat or dog.. you can't be sure to some extent what they will or will not do over longer periods. Laughs.
( knows full well this thread could get explosive. )