Welcome!
In my professional experience, genetic testing is not a generally-accepted practice in neuropsych evaluations, especially for GT (sometimes it is for intellectual and developmental disabilities, as there are well-researched chromosomal and genomic abnormalities associated with many forms of ID or DD). The genetics of intelligence is complex, and poorly understood at the sequence level (although it is well-established that a large proportion of intelligence is heritable--nature rather than nurture). The state of the research literature does not support drawing conclusions on intellectual function from genetic testing (outside of the known pathologies). I would take any predictions of learning style or capacity based on genetic testing under the loosest of advisement.
This is, of course, purely speculative, but honestly, it seems more likely to me that your prospective evaluator is participating in some kind of pilot study/data-gathering exercise with a genetic testing company, and recruiting study participants from among their clients. If that is the case, participation would, of course, be a question of what your family chooses to contribute to this type of research, keeping in mind many of the caveats associated with non-targeted genetic testing in general, such as those you named.
