If we take the classical position that words point to real things in the world, "useful label, loosely agreed to out of convenience" is kind of just regurgitating the meaning of "word". The first half indicating the function, and the second half accounting for the fact we live in a world with a continuum of linguistic disparity.

Now, this position isn't the only position. But a relational model of language for example takes his assertion to an even more extreme place, and suggests they don't function as labels at all.