I disagree. Human intelligence is clearly misoptimised for many goals, and I see no clear evidence that it's easier to design a new intelligence from scratch than to optimise the human one.

They have very different possible effects "FOOM!" vs. "We are awaiting GFDCA [Genetics, Food Drugs and Cybernetics Administration] approval of this new implant/chimerism/genehack", so the average impact of human-optimisation may be lower, but my probability estimate for human-improvement tech is much higher.