Seems to me that it is likely due to the magnets on the hinge of the bottom laptop connecting with the bottom part of the top laptop. The top laptop then treats it as if the lid is closed.

Thanks for sharing about this, That’s really quite a cool and inspiring story to hear regarding the development of the platform and specifically the nature of the people and connections who made it possible. It might have been a bit of a risk but it seems unlikely that the platform would have scaled as well without outside help.