According to Apple's website the Macbook Air appears to only have 7 active GPU cores. I suspect that chips in the Air may be binned separately and may or may not support the higher clock speeds even with the active cooling of the Mac Mini and Macbook Pro.
My guess is maybe this is a yields thing for Apple Silicon? They use the same chips for Air and Pro, but shut off a faulty gpu core that didn't pass QA? Or a temperature thing.
That left me wondering if there are different variants of the M1 with different core counts.
(Note: It always said 8 CPU cores)