Automatic vents for crawl space? – GreenBuildingAdvisor

My builder proposes to install automatic vents in the crawl space of a small cabin in Maine.  He is proposing a slab with 2 feet of cinder blocks, 2″ of foam under the slab and outside the cinder blocks.  The vents say

The Foundation Auto Vent Replace manual vents. Fits standard 8 X 16 inch vent openings. Automatic replacement foundation vent for ventilating crawl spaces. Automatically fully opens at approx.70°F and closes at approx.40°F. Saves energy and lower risk of frozen pipes. Helps prevent foundation decay. 57 square inches of net free ventilating area. Quality you can trust.

While I understand the energy saving, for moisture control it seems backwards.  In the summer it lets in warm humid air that will cool and deposit its moisture.  On the winter the only air in the crawl space will have come from the warm house and it will cool and deposit any moisture.  What am I missing?