كَلَامٌ بَلِيغٌ — discourse judged to be rhetorically appropriate and effective.
مُتَكَلِّمٌ بَلِيغٌ — a speaker possessing the relevant expressive ability.
These are two levels of evaluation. Baligh discourse is an actually produced utterance; a baligh speaker is evaluated for the capacity to produce suitable discourse.
A person might provide an excellent concise answer in one setting. That single success does not establish equal mastery in every topic and circumstance.