Difficulty memorizing times tables is quite consistent with his personal weakness in math fluency. I would suspect that he may have some vulnerabilities with regard to automaticity or retrieval fluency skills, based on the pattern of which skills are personally lowest. (spelling is also affected by automaticity skills) However, if it isn't interfering with his overall growth, development, and enjoyment of school, I would probably keep an eye on it, but not rush into an intervention.
I will note, again, that there is no measure of written expression. There is also no measure of reading or writing fluency, which means that, as well as he is performing at the moment, it is not clear if there are factors that may affect his school and personal success when demands for lengthy, complex, or rapid written language or calculation output become greater over the next few years. That's what I would monitor.
Sharing with the school depends largely on available resources for either GT extension or academic support (though it is unlikely that most systems would qualify him for academic support with his Average-to-Above academic profile). If there isn't anything to be gained, and where he appears happy where he is, there probably isn't much benefit to sharing with the school. If he is ever evaluated by the school for either advancement or support, though, do share these results. Responsible school-based examiners can design and execute better evaluations when they have access to all available data.
