The menu bar is white - or usually so - so there.
I honestly don’t think it’ll be any more distracting than the black notch.
If the black notch is hidden by the more pro-y dark mode usage, then a white notch should be hidden by what most folks in that market/crowd are probably going to use. I don’t know a soul who uses dark mode in their Mac. The bulk of Mac users I know are non-pro “regular users, so they’ll have white menus until the day they die, as most MacBook Air type users will. I think the problem pretty much solves itself and that a white notch will likely prove less noticeable on a device where most users keep the traditional Mac look.
Update: I just realized/remembered the default macOS settings allow for translucent menu bar taking on the coloring of whatever desktop image is in place. So it’s be no different/worse than the black. It’ll just be part of the overall bezel/framing look, except off-white on an Air instead of black. And if people turn that setting off to where the menu is white at all times, the notch will be hidden quite nicely.