They're just interline agreements. I can't imagine allowing mere interline agreements to dictate scheduling.

I also can't imagine these are generating any material level of traffic for WN. I just searched TPE-LAS and TPE-SAN on google flights and it did not return a single flight with a WN segment. The fact is that BR and CI both have US alliance partners (UA and DL) and that's where virtually all of the connecting traffic will go