Bottomless bottom boards in vogue

A French exhibitor shows his bottom board designed to inhibit varroa development. I think the idea is that when varroa fall from bees they fall out of the hive and can't jump back on bees. Apparently the bees won't propolize the plastic tubing and inflow of air causes no problems even in cooler climates. I suppose it makes sense for varroa treatments that repel but don't kill varroa.