It's usually best if the Ubar's wishes are followed, of course, as a show of trust in his judgment. However, a private owner's specific directives are usually honored, unless those commands are in direct opposition to a basic room rule. For example, all privately owned slaves should still adhere to the rules for entering and leaving our home, following the correct serving order, greeting properly, and so on. In the case of serving restrictions, such are usually left to the discretion of the owner. After all, that is the owner's personal property, and her body and how that body is used -- whether being used sexually, being fed by another's hand, sitting on another's lap, being pm'd, etc. -- is the owner's right to dictate.
And my Master shares my conception of this. (He was about to post exactly this same thing and decided I could add his opinion for him to save his time and effort -grins-.)
Of course, we could both be wrong, but that's always how we have seen the line drawn in the past.