This is not a bug because the Murata thermistor chooses the default values of the TGAIN and TOFF. When the default values are chosen, the nTGAIN and nTOFF registers are cleared to make the NV memory space open for user memory, and the default values are loaded from ROM instead. If you choose the third option in the list, or pick a non default value, then the nTGAIN and nTOFF will be set with their custom values, and the enTGO bit will be set.