Val, the difference is that ID'ing privately for diagnostic purposes is a means to an end, namely securing appropriate educational services. A skip/acceleration is the manifestation of those services.
I would hope that true GT students' abilities would be validated by parents *regardless of the presence of a diagnostic*. HK's daughter is an example I have in mind-- she's clearly PG, and so her parents don't feel the need to seek external validation of her giftedness. She also isn't being publicly identified at her school as gifted. I daresay she is both aware of her PG abilities and is made to feel valued because her achievements are a tangible manifestation of her control over her innate ability.
An implicit assumption in your argument is that people cannot feel validated for an innate trait unless that trait is identified publicly. Maybe we can explore that assumption.
