We've asked Apple if it can elaborate.

The iFixit team has speculated that the sensor might be more sophisticated and track both the frequency and angle of lid openings to help the company diagnose certain problems -- say, stress on the display cable. It might have an easier time pinpointing systemic flaws.. However, it's not clear that's the case. For now, the one certainty is that Apple has used the 16-inch MacBook Pro as an opportunity to refresh many aspects of its design, not just obvious changes like the screen or cooling.