If it is mandatory, it must be mandatory in a profile. A feature which is optional or conditional in the base standard could be mandatory, optional, conditional, or excluded in the profile. It might say that only the simple form of record composition name may be used, and not the complex form. It might exclude the use of the Delete service. Either of these would be a narrowing of the scope of the standard, which permits an implementation to choose to support or not support the use of named result sets.
Exclusion is the source of some confusion.
Exclusion of a feature by a profile does not mean that an implementation which supports that feature does not conform to the profile. This means that participants using the profile have agreed that when they are operating according to the profile, named result sets will not be used. For the origin system to conform to the profile, it would need to be configurable to operate in a mode in which it would suppress transmission of non-default result set names.