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In the special group studies, the mean PSI scores for the gifted on the Wechsler family of tests have historically fallen in the High Average (110s) range. Solidly Average scores such as your DC obtained on the one PSI subtest administered (likewise the one WMI subtest) aren't a red flag in and of themselves, but may have additional clinical meaning in a larger context.
The extended norms very well may affect the GAI and FSIQ, if the VCI rises that much. You still have MR, too, which may be impacted by the ExNorms.
The GAI-CPI (WMI & PSI composite) difference is substantial enough that NAGC is recommending that a much broader range of Indices other than FSIQ be used, especially for 2e students.
https://www.nagc.org/sites/default/files/Misc_PDFs/WISC-V%20Position%20Statement%20Aug2018.pdf
