A USB hub is designed to be used with a single USB host and multiple USB devices.  An iPad Pro, desktop PC, and laptop are all USB hosts.  The ADI-2/4 Pro is a USB device.  So, for example, the hub would allow you to have a single host like a desktop PC and use it with multiple devices simultaneously like an ADI-2/4, a keyboard, mouse, MIDI keyboard, USB thumb drive, etc.

In order to switch between multiple USB hosts with a single device as you describe, what you're looking for is a USB switch. Sometimes they're called KVM switches because historically the purpose was often to have a single keyboard, monitor, and mouse which you could switch between multiple computers (KVM = Keyboard, Video, Mouse).  KVM Switches date back to the days before keyboards and mice used USB.

I can't see any reason why a USB Switch wouldn't work with the ADI-2/4 Pro.  It's essentially equivalent to physically unplugging and replugging the USB cables.  Often it's sluggish and it takes a few seconds for the various devices to reconfigure themselves, but it should work. 

Note that with the iPad Pro, however, you do need to pay attention to where it gets its power from. If you plug a USB switch into the USB port it won't be feeding any power into the iPad to charge it.  In fact it will most likely be draining some power from it.  In that case you may need to try and combine a device to merge power and USB into the iPad with a USB switch which starts to get more complicated.  A Magic Keyboard for the iPad might also solve the problem by charging the iPad through the little pins that it connects to without requiring you to supply power through the USB port.