[circlingthesun]

There is a related video by minute physics about how the RGB color space stores the square root of the brightness of each color channel, because human color perception is roughly logarithmic. Bad color blending is therefore pretty commonplace because it uses the average of square roots instead of the square root of the average of the original brightness values. See: https://www.youtube.com/watch?v=LKnqECcg6Gw

[BeFlatXIII]

This is still an issue on iPhones today. When you have a notification icon and start to pull your Home Screen to make it blurry, the border of the red circle gets inexplicably dark. Whatever happened to Apple’s famed attention to detail. This has been the case since the iPhone 6 was new, if not earlier.

[Asooka]

If you blend values in linear space, you'll linearly interpolate from the starting physical intensity to the ending physical intensity. This is a very reasonable default, corresponding to an objective physical measure. Also it makes your gradient appear roughly the same to people with reduced colour perception. Other modes would be useful too, maybe something that goes through HSB colour space, but I suspect designers would find it easier to design their desired gradient in a program of their choosing that then outputs a piecewise linear approximation.