There seems to be some confusion.
<quote>Many of us are aware of the STM32C103 boards referred to as the "Blue Pill".</quote>
afaik, there is no STM32Cxxx and modules with the STM32F103C8 are referred to as Blue Bill. Probably just a typo, but perhaps indication of sloppy spread sheet reading.
Said that, the batch of 5 (ordered, 6 shipped) I received had indeed a 10kOhm USB pull-up resistor, when you find all over the 'net that it ought to be 1.5kOhm. I fixed one, but still Arduino programming over USB doesn't work (regardless of pull-up resistor value), can't tell, if other USB functionality works. The units can be programmed using the ST-LINK/V2 interface, so they aren't complete duds. I put it aside and used a Teensy LC (considerably more expensive, but works as advertised) for now.
I was wondering, whether the 10kOhm/1.5kOhm mismatch is a SNAFU at the factory which meant to discard the units, but they somehow made their way to Fleebay or whether there's some misunderstanding of the schematic and intended use.