Apologies if this seems like beating a dead horse, but it remains quite an annoying situation.
As @Joris pointed out in Documentation of Editor Protocol, the other view of the situation is that the iConnectivity boxes are MIDI routers, not USB hubs, so it’s equally arguable that they should not forward any other traffic because it’s not any of its business, and who knows what that other data may be. Also, this is not just about iConnectivity boxes, the same goes for any other MIDI-oriented USB hosts and the like.
Me thinks the ideal situation would be keeping the default setup as is, but additionally support the editor protocol encapsulated in SysEx on any MidiHub port (including DIN!), using this would require manually configuring the MIDI port in the editor (so no autoprobing issues). Having such an option would greatly enhance the flexibility - for example with the MIO boxes you could then run the editor from a remote computer over network (RTP MIDI), which would be seriously neat.
On a kind of related note, just tested running the editor over USB/IP, seems to work fine. The caveat is that a local computer connection is still required, but this way the UI is far, far more responsive than X-forwarding over ssh.