Given the definitions of terms ordinary character types, narrow character types, and character types (added by P2314R4) in [basic.fundamental], ordinary/narrow character types aren't "character types that are ordinary/narrow", because signed char and unsigned char are ordinary/narrow character types, but not "character types".

On the other hand, the term encoded character types defined in [fs.req] has the exactly same meaning as "character types". Is there any reason to use two terms to describe the same set of types?

It seems that the term "encoded character types" should be defined in [basic.fundamental]/11, used in [basic.fundamental]/11 and [lex.charset]/5, and [fs.req] just needs to refer to the definition.