That is just it, the port does not support OTG so it would be one power source that would be supplying the USB 2.0 HS (or slower) endpoint device and the VF2 board. Hence why a splitter would only work if the power source supported 5 volts maximum.
Or you could also use that USB 2.0 HS port if you were powering the VF2 using a PoE+ HAT or as @cwt said using 5V GPIO pin(s).