Did Johns actually go that far? AFAIK, he started with some powers as a kid, and they grew and grew as he matured.
To my mind, it's sort of like the "Batman is a loner" argument: Batman isn't a loner, he's got the biggest non-blood family in comics! Some writers keep portraying him as a brooding loner, some as the paternal influence over a whole slew of "bat-characters." It goes back and forth because the audience wants it both ways (when characters like The Question already exist for the brooding loner archetype).
Some writers portray Superman as not having his powers as a kid, some give him his powers as a kid. IMO, plenty of superheroes got their powers as adults, why not let Supes have his powers as a kid?