I can't find any further information on this intel testing like what altitude they perform the tests at.

AMD has perform testing at data centers of different altitudes and there is some statistical significance in SRAM error rates. And that is typically only around 5000-6000 ft msl.

https://dl.acm.org/doi/10.1145/2503210.2503257

Planes are much higher than that in operation so get larger amounts of unfiltered solar flux.

This may be one of the causes of higher cancer rates in pilots, but eliminating other environmental causes may be difficult

https://www.cdc.gov/niosh/aviation/prevention/aircrew-cancer...