It's "perfectly logical" because it can be booked through the system (well, SQ flights need to be booked over the phone). But it satisfies the maximum 4 connections per direction rule and does not step into the North Asia, Japan or Central Asia regions. Back then in 2012 they did allow me to pull a ORD-DUS-FRA-ICN-TPE-SIN oneway ticket, my first foray into flying F and hitting up the Lufthansa FCT. Such fond memories... They are in fact pricing out MEL-PEK-TPE/TSA-SHA-HND correctly for me at 40k in J for a standard North Asia ticket. Even with the changing airports in Taipei. I could do an airport change in Shanghai too if I wished, but TSA and SHA are much more accessible than TPE and PVG. Particularly useful since I have friends to meet in Shanghai and Taipei for dinner, and Tokyo is a good landing spot for me to pull a NRT-AUH-BOM AA ticket on EY to get my haircut in AUH and fly the A380 Apartments, even if it's on a short trip from AUH-BOM. Just because NRT-AUH-BOM falls within the 125% MPM rule that AA has on its award tickets.