That section in the lower left of the board looks like a component was removed from the production design. My guess it was another sensor type that didn't work out.
The pic of the board connecting to the battery in Step 13 has a glaring unused section of board shown in the lower left. This is not common board layout practices. My guess is that an IC was removed from their DVT units before this PVT shipped and they didn't bother to re-route. My guess is that it was either a wireless chip or additional sensor that did not work out with the DVT step.