When I changed to use P3 wide colors in our app, I noticed that the gradients didn't use that color space.

I looked through the code and saw that MKGradientGenerator uses CGColorSpaceCreateDeviceRGB. I changed that to CGColorSpace(name: CGColorSpace.displayP3) and the gradient was displaying in P3.

Maybe you can add a parameter (with default value) or get the color space from the start/end