just talked to a buddy who just got a new XXL evo (like just off the ship) he said it is not on the new ones because it was only there for letting air out while putting the top down and he was told to just leave the flaps on zipped.
Have been in contact with the company on this myself. As mentioned above, the vents were there to help avoid condensation and to vent trapped air when closing the shell (making it easier to close). Now the tents are vented at the top, and the company recommends leaving walls and windows open when closing (red marks tell you where to leave the zipper pulls)--making those bottom vents redundant.
The company was thinking to remove them entirely, then realized (in part through customer feedback) that they lend a sort of signature look to the brand. So while you may find a few bottom-ventless examples in the wild, expect most newer examples to sport them, if only for aesthetic reasons.