It's only a surface contradiction. Because there are infinitely many-ideas but only finitely-many words, anomalous lexical constructions, of which glaring surface contradictions are a prime example, are bound to occur. The idea being aimed at by this particular expression is that there is great overlap, but not actual identity, between the 2 notions. I don't know why this expression is so prevalent (wouldn't finding out take some kind of exhaustive survey?), except that perhaps because it sounds like a cool thing to say, especially among people who think that eating at McDonald's is a status symbol.
Panning out for a wider perspective:
The fact that, for non-trivial situations, perfect order is impossible (and ditto for perfect disorder) is a theme within Ramsey Theory.