>So you just use a larger low dpi icon. The problem is that the icon at the same physical size now has much more details and looks less clear.

In what way does it look "less clear"?

The problem with showing more details on the low-dpi screen for a 16x16 icon was the low resolution of the screen.

A hi-dpi screen doesn't have this issue. It's effectively showing 32x32 quality on the 16x16 "virtual pixel" size.

At worse, it would have looked as good as a 32x32 icon in a low-dpi screen. But in the hi-dpi it looks even better, much sharper and refined. You're getting an icon that's as good as a 32x32 icon would be on a low-dpi screen, but with half the physical size, so that it appears twice-as-detailed as a 16x16 icon would be.