Confused as well. The sketch shows that all its using Serial, Serial1 and Serial2 and USB MIDI.
I think you are talking about USB MIDI not being available? If you look through other posts on USB Midi for the T4 you will see that PRJC is working on USB Midi as well as other USB drivers operational. Have no time frame.
Now with that said you know that the T4 is not drop in compatible for the T3.3 so if you are planning to use the PCB that is shown in the instructable you will not be able to.