There is also research questioning whether SB5 is a best measure for some highly gifted kids. They had kids who scored I think it was a mean of 135 on WISC-IV and were placed in gifted classrooms; a significant proportion scored twenty or more points lower on the SB5. Anecdotes and achievement supported the WISC scores.
Also, that's around the age we first realized my DS had a significant vision issue with one eye and general far-sighted. His SB5 had significant impacts in non-verbal versus verbal similar to yours. Clues we should've noticed were an inability to catch, find things on the ground, difficulty looking at people who were too close to him, minor clumsiness, and a tendency to skip words when reading.
If you observe some of those things, you may also want to see a developmental optometrist or opthamalogist to rule out vision as a factor.
