44.1 or 48k usb2 or 3?

I have noticed in the ASIO driver window if you choose 44.1k you have an option for usb 2 or high speed usb 3.
If you choose 48k as I use all the time the high speed option is greyed out. What does this mean exactly?

never noticed that but I wouldn’t worry about it at all you’re not losing any performance.