Don't read too much into it. There is an APU bleed elbow on one side and the other is the external connection. In the middle is a low pressure air connection. It has to go somewhere!
Tradional to start right to left starting away from the steps/ pax. So the external air is on the side that means you start in an unusual order- as it's an unusual event ( well, on NGs it is)... So logical the layout is as it is.
Drawn up in 1965 from existing parts, it's quite a historical design anyway.