FWIW, and in reference to my earlier question, it looks as if TIMATIC has been updated, at least via UA. And it appears that I can do TPE-PVG//PEK-MUC, with PVG//PEK via train. If BR gives me a hard time at check in, I'm assuming that if a problem, I can be switched to TPE-PEK.

240-Hour Visa-free Transit Program for Entry

Nationals of USA can transit without a visa for a maximum of 240 hours, starting from 00:01 on the following day, at one of the following entry points:
...

Beijing - Beijing Airport (PEK), Daxing Airport (PKX);
...

Shanghai - Shanghai Hongqiao Airport (SHA), Shanghai Pudong Airport (PVG), Shanghai Port;


They must have a confirmed onward ticket to a third country. They can make cross-province and cross-city visits in the above areas.