Yes to everything that aeh and polarbear posted.
Just wanted to add that the GAI isn't a separate test - the scores from parts of the WISC are used to calculate it. With the WISC-IV it was 2 out of the 4 (excluded working memory and processing speed), I assume with the WISC-V it would use the first 3 out of the 5.
I also have a DS that we tested when he was 6.5 because the school was convinced he was ADHD. At that point he tested gifted/probable LD which made sense with what we saw/experienced with him. We recently retested (he's almost 9 now) to confirm the LD (which it did) and his GAI was way higher this time around which made even more sense.
As noted above there are a lot of possible explanations that can result in a similar test profile. Welcome to the club
