The names given to the code rule types are misscleading and non descriptive. I can not see Extensional as a direct synonym of explicit and Intensional as a direct synonym of implicit. Moreover, the difference between these rules is just that the former specifies individual codes and the latter the sets of codes.

By definition an extensional definition of a concept or term formulates its meaning by specifying its extension. Thus both of these rules are extensional. Moreover, in logic and mathematics, an intensional definition gives the meaning of a term by specifying necessary and sufficient conditions for when the term should be used. So also, even if applicable, I would see both rules identical in the sence of intensionality.

So my suggestions are:
1. Do not give double names, such as Extensional (explicit), use one name
2. Change Extensional and Intensional into something that reflects the true nature of the rule such as Single code rules and Set code rules

Existing Wording:

Extensional (explicit) code rules are used to include or exclude specific codes in value sets and code systems.

Intensional (implicit) code rules are used to include or exclude sets of values in value sets.