This removes the gray background for me on a compact style date picker: datePicker.subviews[0].subviews[0].subviews[0].alpha = 0

I've just got my m1 air and had this same question, short answer is no I believe other that removing iPad. Targets Target General Deployment Info macOs - check Mac and you will get the dropdown to select "Scale Interface to match iPad" or "Optimise interface for Mac"