I don't think it's really that Android design is more "okay." I think it's that the iOS (and moreso macOS) icon design-language has the potential for some really distractingly-beautiful outlier icons — icons that really twig on people's "gathering fresh ripe fruit" reward system. And when there's some of those sitting on your Dock as part of your every-day experience, you start to both:

1. want every icon to be as tantalizing as those icons already are (and so desire to customize the "lesser" icons to achieve that); and

2. feel like something very precious has been lost whenever an icon is made less tantalizing.

I would hazard a guess that the "greyscale makes people less addicted to their phones" research is more true for iOS users than Android users. iOS just has a higher average level of visual addicting-ness in its design. (Which, to be clear, has nothing to do with differing levels of "polish" or anything like that; addicting-ness is its own thing. Some [good] design-aesthetics have it; other [also good] design-aesthetics don't.)