Noam Chomsky’s famous example ‘Colorless green ideas sleep furiously’ shows that a clause doesn’t have to make sense in order to be grammatical. Some 85 years previously, Lewis Carroll had shown much the same sort of thing when he wrote:

> 'Twas brillig, and the slithy toves  
Did gyre and gimble in the wabe;  
All mimsy were the borogoves,  
And the mome raths outgrabe.

Similarly, to say that someone desires ambiguous brevity is also grammatical. Whether it makes sense is another matter.