My board has two controllers and both shows the same behaviour.
lspci|grep "USB controller"
00:14.0 USB controller: Intel Corporation 200 Series/Z370 Chipset Family USB 3.0 xHCI Controller
08:00.0 USB controller: ASMedia Technology Inc. ASM1142 USB 3.1 Host Controller
My board has two controllers and both shows the same behaviour.
lspci|grep "USB controller"
00:14.0 USB controller: Intel Corporation 200 Series/Z370 Chipset Family USB 3.0 xHCI Controller
08:00.0 USB controller: ASMedia Technology Inc. ASM1142 USB 3.1 Host Controller
Asus PRIME Z270-K, BIOS 1207 06/22/2018