I believe "they" are drawing their conclusions from breeding BP's for 20+ years, and doing so with Spiders when there were only a handful of them known to be around.
Not everything that happens in this business is publicly advertised information, so just because you don't see a Harvard study on it doesnt mean anything one way or another, but I like and trust the information I have heard first hand.
Next we'll be breeding for Super Desert females.....