Is HKG-TPE-TYO-HKG valid then? Both HKG and stopover TPE are in Zone 3, but still can't price it out online and errored out after selecting final flight segment.
Perfectly valid routing.
I got
02Sep HKGTPE BR828
09Sep TPENRT NH824
16Sep HNDHKG NH859
23000miles + 14770 JPY in Y