I'm thinking that makes sense. Position 3 is the neck pickup plus one coil of the humbucker. When the push/pull is down, the humbuckers link wires go to the switch where they are shorted to "hot". That gives you the coil between the link wires (serving as "hot") and ground, which is the outer coil. This hums, which means that the neck pickup is not RW/RP relative to the bridge pickup outer coil. When the push/pull is up, the link wires are shorted to "ground" and disconnected from the switch. This give you the coil between hot (which is still live on the switch) and the link wires (serving as "ground"), which is the inner coil. This is hum canceling, which means that the neck pickup is RW/RP relative to the bridge pickup inner coil. There's no change when actuating the push/pull in position 4 because both the push/pull and the switch short the link wires to ground, giving you the inner coil either way.
Given that a particular single coil and humbucker are in-phase, the single coil will be wound with the same wind direction and polarity as one coil of the humbucker (not hum canceling), and with the opposite wind direction and polarity of the other coil (RW/RP = reverse wind/reverse polarity = hum canceling). This is why positions 3 and 4 cut to different coils: the neck and middle are (theoretically) RW/RP to be hum canceling with each other in position 2, which means that each will be hum canceling with a different coil of the humbucker.
Thats my read on it anyhow!