U2725QE USB hub recognized as 2.0 when connected to MacBook Pro

Here are some follow-up results on the problem where the U2725QE monitor provides only USB2 speeds (at best) when connected to a Mac by Thunderbolt:

1. To clear the problem, the monitor needs to be started (or restarted) after the Mac has begun loading the OS. 
2. Simply cycling the power button on the back of the monitor, with a pause for 6-8 seconds, will clear the problem. Devices would have to be unmounted manually (‘Ejected’ in Apple-speak).
3. Turning on MST (Multi-Stream Transport) restarts the monitor, just like power cycling. As some contributors here have noted, the effect is temporary and only lasts until the next restart of the computer. Again, devices would have to be unmounted manually. 
4. To demonstrate that MST is no solution to the problem beyond restarting the monitor, note that turning MST from on to off has exactly the same effect as turning it from off to on.
5. The advantage of clearing the problem by restarting the Mac and power cycling the monitor during the restart (as I suggested in an earlier post) is that the OS will unmount the devices and otherwise tidy up before the restart.
6. The additional advantage from a cold start of turning on the computer first and then the monitor after the startup chime is that no additional starts or restarts are needed.
7. The problem does not occur when connecting the monitor by HDMI or DisplayPort, with the USB connection made through the USB upstream port. But that, of course, defeats the objective of a single-cable connection.

I’m still looking to Dell for a proper solution.