On the iPad the MIDI Track on the Arrange page suffers from the same non-scrolling, non-synching with the main track as occurs on the playable tracks on the Create page. Also in common with the other pages is that the scroll bars on the midi track are nearly unusable on the iPad. Hopefully these issues are on the radar for 3.3.
I discovered that the Midi Track does scroll and synch with the Main Track if you select a motion clip first. If you have a performance track that is broken up into many clips, the midi track will only scroll through the clip or clips you have selected. The midi track will scroll through the entire composition if Select All is chosen from the performance track menu. However if the performance track is selected by touching the left side of the track, the midi track is not enabled. My suggestion would be to synch the midi track to the main track for the performance track that is selected without having to select a clip. This would be more intuitive for a person that is used to a DAW where a piano roll view scrolls with the selected instrument track without having to select any particular part of the instrument track.