My older son is 2e (Aspergers) and I often wonder if his scores would be higher if he wasn't so anxious and didn't have problems with novel situations like testing with a strange person. He tests gifted and qualifies for school services but he didn't blow the test away (and they didn't use a WISC or SB so I really have no idea how to compare RAIS, which is a really short test, scores to a WISC.
My younger son I denied that he was gifted for years. Then I accepted it. Then the school tested him on the K-ABC II (why this school system won't use a darn WISC is beyond me)...and he came out profoundly gifted...that I didn't believe. I had him tested at the college and the WISC was slightly lower (not enough to qualify for DYS but close) which was much more my inclination. I did not take the second testing into school and will continue to let them think he is profoundly gifted if they want to (not going to argue the point "my son isn't as smart as you think he is" is just a silly position to take).