Great, we can just go ahead and file that in the garbage with the rest of the anecdotes. Notice how everyone who is happy with their diet says the same thing you just said, no matter what their diet is?
Unfortunately there is not a whole lot of research on ketogenic diets outside of treating cognitive diseases. But it can be argued that if it helps prevent them in people with declining brain functionality, it improves brain functioning in healthy people.
That could be argued, but the counter argument would be "that's a completely baseless and unfounded argument". And there isn't evidence that it helps prevent disease in people with declining brain functionality. Your link says "we should do some research on that" not "there has been research on that".