I have both miniLED MacBook Pros and 13" and 15" M2 Airs and the pros do not have better white balance or uniformity over the M2 Airs.
I've seen a few Pros that have shifts of green or dinginess to the left or right, or slight splotchy areas (those were returned). I also think that the pros have some sort of film over them (perhaps the anti-glare layer) that gives a bit of a shift in color - slight pink or dingy green when looking off angle a bit (most noticeable on whites). This is not the case on the M2 Airs.
I've found that the miniLED displays in the Pros are superior to the M2 Airs only due to the awesome black levels and ProMotion. While they may be better spec'd on paper, to my eyes, all else is on-par with the M2 Air displays (contrast, color vibrancy, pixel density to the eyes, white balance, and so on).
Having said all that, there are going to be varying quality levels from one panel to the next - even within the same exact model line. So perhaps that's just what we're seeing here. No one is escaping the display panel lottery by choosing a MacBook Pro with miniLED.