Consider the argument for his proposed language being Turing complete on the flow manifesto page. He claims that this follows from the Böhm-Jacopini theorem. However the Böhm-Jacopini theorem requires variable assignment is allowed in the subprograms (which does not appear to be the case in flow), and without this the theorem does not hold, as this paper by Kozen demonstrates: www.cs.cornell.edu/~kozen/papers/bohmjacopini.pdf. Then he goes on to argue that order duality implies the existence of a selection operator in flow, which doesn't seem to make any sense.
I think it's telling that he has been working on this since 2010, yet has no decent proofs of his claims, nor any working implementation.
As far as proofs or working implementation, sometimes life gets in the way of progress :-)