Ah, the topic question:
Those extra battery terminals **should** be I2C - -
But since the device uses an external battery management chip (on one of the SPI buses), then it is unlikely that the battery includes a battery management chip.
Most likely, that I2C connection is just the battery temperature sensor.
That is because to "properly" charge Li-Ion, the battery temperature changes have to be monitored to detect "full charge" condition (you can't use terminal voltage detection to reliably re-charge Li-Ion).