I am wondering if this is a case of "all men are mortal, Socrates is a man, therefore all men are Socrates."
As in "Anai did this, and Anai is a champion, therefore everyone that does this will be a champion?" is that the supposition? Can we even suppose the flip side, that "only people that do this become champions?" Can we find exceptions, people trained by other methods who ultimately kicked butt ... like recent local guest Miss Yoko Tanabe who was a shot-putter?
So again, focus from a young age on a short list of techniques that seem to fit the projected ultimate size of the up-and-coming teenage star might work ... it is indeed what successful producers of Olympic results tend to do. But that doesn't mean ... and I don't think the OP meant to imply ... that every child who is trained by this method is going to be a killer judoka. I'd suggest certain weakness to this approach, as other have here, that in a small sample of students the likelihood of getting it wrong is high. With a large number of candidates to put through the grinder no one might notice the mistakes and one might indeed produce proficient and confident competitors. It does not mean that a child trained with a wide range of judo techniques or one trained as a wrestler can't succeed in judo competition ... because there are many examples to the contrary.
If there is a common factor, one essential element it is temperament. It includes what AnnMaria calls the "want to" that can't be added. I'd amplify that in her case and in the case of one of her family members, and in the case of many competitive champions, as a deep-seated and tearful "need to" which I have witnessed first-hand. A "need to" and a risk-taking nature. The rest ... to paraphrase the prophet Hillel ... "is commentary."