Note sure this is a good justification, but it's the only claimed advantage I could find in their main paper:
> 2) Unlike space-based observations, the Moon provides a
large stable platform for maintaining astronomical instruments in permanently stable configurations. The rotation
angular velocity of the Moon is about 0.55″/s, which is
about 27 times slower than the Earth. The slow rotation
allows long term monitoring without interruption for as long
as about 10 days.
> 2) Unlike space-based observations, the Moon provides a large stable platform for maintaining astronomical instruments in permanently stable configurations. The rotation angular velocity of the Moon is about 0.55″/s, which is about 27 times slower than the Earth. The slow rotation allows long term monitoring without interruption for as long as about 10 days.
http://link.springer.com/article/10.1007/s11433-011-4255-7