Apple Motion exports an animated flat background illuminated with Spot or Point light + falloff with bad banding

In Apple Motion (5.2.2) I use a Point or a Spot light with Falloff on a flat animated background. In the Canvas it all looks great, no banding. (There really is no banding on my display, unlike on this page where I can see some, thanks to crap Google conversion of my image.)

When I export to ProRes4444 or 422, whatever, and I play the file into QT or FCPX it has banding all over.

What the hell is this?

I have to add noise onto my background to get rid of the banding, but I should not have to do that with 10 bit output & Best settings. It's there no matter the color, more visible with blue.

After Effects outputs a CLEAN gradient in a similar setup: spot light on a flat bkg., CLEAN as it should be.

What's with the crappy Fallout Spot and Point lights? Apple FIX THIS please!