As above, hence my previous post. It is a powered hub, it is doing what it was designed to do. Maybe it was not designed "well" in that maybe there could be a switch on the dock to turn on and off the usb power, but it's the way it, and nearly all, are designed. Possibly for a good reason.
And to me, the dock is not to stop me having to plug in or unplug a cable, but rather 4-6 cables (audio, power, usb hub, dongles, video) and the inevitable tangle all those cables will eventually create. I'd have no issue unplugging one usb cable.
Also, you'd have to take action to turn off the usb power, which in terms of effort and time involved would be very little different to just unplugging one usb cable.