It has to do with the way they designed the catch can but it returns oil to the center of the block. Here is the link with their explanation of the design.
The Original Air/Oil Separator – Crawford Performance . It worked well on my Subaru but I was also running a rotated mount GT35R setup so a catch can was required.
I like that one from ConceptZPerformance. That's most likely the ones I will go with. Thanks for the link!!