I have a midi2+ that I use to connect Norns with another host which I think functions very similarly to the mio2. On Norns, in the midi devices I see 4 different midi devices labeled “iconnectmidi2+ 1” through “iconnectmidi2+ 4”. By default each of these options connects Norns to only one port. “iconnectmidi2+ 1” routes between Norns and din pair 1, “iconnectmidi2+ 2” routes between norns and din pair 2, “iconnectmidi2+ 3” routes between Norns and the other usb host, and “iconnectmidi2+ 4” is unused.
The thing to realize though is that this 1 to 1 routing is just how the port routing is set up by default - they are however completely configurable. So if you use the iconnectivity software you can make a configuration where “iconnectmidi2+ 1” sends and receives midi from norns, din1, din2, and the other host.