Neither did I!
This guy really mangles Smith and confuses a lot of the claims of neoclassical economics (HT - Peter Boettke). It's assertions like this (by a non-economist, I should add) that feed Boettke's (in my view, wrong) criticisms of mainstream economics.
I don't see how you can read Smith as implying some optimal general equilibrium. Smith argues that by pursuing private interests, economic agents promote general welfare. This is obviously true whether a "perfect" Arrow-Debreu general equilibrium holds or not. Identifying the two with each other is a mistake. The contribution of Arrow-Debreu was to rigorously demonstrate the general equilibrium outcomes of a certain type of model of the market that is (rightly) widely in use. Any departure from that optimum ought not to be confused with a non-existence of the invisible hand forces that Smith referred to.
Confusing Smith's claim with Arrow-Debreu's claim leads to inappropriate conclusions that because we've departed from a neoclassical optimum it means that the market "doesn't work" or has "failed". That, I think, is the wrong way of looking at it.
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