Perhaps not a popular opinion, but the overwhelming majority of "gifted" kids seem to be near the middle of the bell curve with parents that are convinced little George is the next Einstein.
It is kind of fascinating since it does seem plausible that treating a child as gifted with high expectations and then providing focused, advanced instruction may be a self-fulfilling sort of situation.
I used to think "gifted" implies there is some natural high intelligence, where in reality its the children of well educated and/or motivated parents. Honestly now I think both benefits from segregated education so I dont really care about the distinction.
I have thought that selection for "giftedness" in young children is multi-factored with a combination of "exposure" and innate aptitude and curiosity of the child at the very least.
If you take "exposure" to mean the child has been introduced to a multitude of concepts and experiences both at their age-appropriate levels and grades above, the conjectured distribution starts to make sense. Wealthy children or those of highly educated parents tend to have incredibly high "exposure" increasing their representation in gifted programs. Those not from such a background will necessarily need to be highly curious and/or have high innate aptitude.
For the lower grades, gifted kids regardless of background will be in the upper decile of scores. As they grow older and "exposure" differences across the entire population minimize, those who were gifted only due to "exposure" will fall to the middle of the curve. Those with high curiosity/aptitude will continue to be in the upper decile, with those who had early and continued high exposure (usually a result of wealth or parent motivation) in the top percentile.
To your point, if you believe the goal should be to meet children where they are and advance them, this model isn't horrible. What it does point out is that there may be a fair amount of top percentile talent that is unrealized due to lack of "exposure" and resources.
It is kind of fascinating since it does seem plausible that treating a child as gifted with high expectations and then providing focused, advanced instruction may be a self-fulfilling sort of situation.