Earlier quoted context omitted.
(edited for source) There is no such thing as a free market: it is an idealistic theoretical construct. And even if it were real, it would only be efficient if P=NP[0]. 0. http://arxiv.org/abs/1002.2284
Your point is technically true, but you can consider it an idiom for either "maximally free market" or "sufficiently free market".
In some cases, even a nebulously defined "sufficiently" free market is impossible.