Windows HiDPI support is funny. If you boot into 200% 2160p mode, all your icons are full-size. If you switch to 100% 1080p and then back to 200% 2160p, some of your icons become twice as small. You returned to the exactly same settings, yet some icons are now smaller!
Apparently, this can go even further. If you switch display modes back and forth a couple more times, some icons might become 4x as small!