Did you see my post 17? I really don't need a degree to see how kids naturally learn to read. (I have a bunch of other degrees though...)
I can put my anecdotal evidence against yours.
My first grade class had 52 pupils of assorted intelligence and ONE teacher with no assistant. We all learned to read phonics first in half the year. By the end of the first grade we knew how to read, and not just certain level basil readers, but anything we came across.
Meanwhile, our friends in public school learned to sight read and by the third grade could read silly Dick and Jane stories.
This went on year after year.
Written language is coded language. Learn the code, you learn to read. It’s been that way for 3500 years, because it is human engineered method of learning.
Maybe your genius kids were able to guess the code all by themselves, but they are the exception.
Analogy would be to musical notation. Some rare folks can play by ear, but most people have to be taught.