I doubt this is true. There are smarter people and there are simpler ones. I guess they're in the same ballpark WRT energy usage. Could you turn the latter into the former? Why not?
I suppose anything is possible, though that may well be much more challenging if intelligence is a function of the physical configuration/arrangement of the neurons in the brain. The interesting question if the structure theory is true, is what kinds of effects that would have on the sense of self, and of consciousness as a whole.
But that's a different question, isn't it? We are talking about "overclocking" the brain, so to speak, not necessarily making one smarter or dumber. The speculation here (if I understand correctly) is that "overclocking" the brain has a cost somewhere, but that doesn't imply that smarter people are running "overclocked" brains per se.