After some searching, I will answer myself.
The announcement of STM32G0 came in December, while the chip was manufactured in week 38 (August), 2018. It is definitely an early sample. The silicon might be the same as current production version, but the early engineering sample documents are not public. Anyway, label says it's revision B, which has the following errata.
However I haven't read the REV_ID yet ( REV_ID[15:0] bitfield of DBGMCU_IDCODE register ) to confirm it is 0x2000 .
David
