The adjective baligh is used of both discourse and speaker, but its referents differ: one concerns the quality of a particular utterance, the other the speaker's power. The passage alludes to using a shared expression in its meanings or explaining the usages by interpretation.
Baligh discourse: an actual sentence or text that is fasih and suited to its context.
Baligh speaker: a person who possesses the faculty to compose such discourse.
The shared label must not erase the conceptual difference between the quality realized in speech and the enduring capacity of its author.