Clarity absolutely does not stem from brevity. Brevity is good, but it pushes toward ambiguity, not clarity.
For example, consider spelling a word. The briefest approach is to say the names of letters. But these are similar, often differing only in one phoneme. E.g., P and B differentiating sounds are both bilabial plosives, differing only in whether they are voiced. But people for whom clarity is important will use something like the NATO Phonetic Alphabet. There, you'd say "papa" and "bravo". [1] It is much less brief, but much more clear.
We might have a different view on what "brevity" means, then. The ITU/NATO alphabet you mentioned is a prime example of brevity. Other examples include those used by air traffic control and fighter pilots.
