If you had the sail kit the "nub" serves as the sail anchor point.

Speaking of Nubs, I think the issue of a drain plug that is pulled to drain butt water (when it's closed) is interesting.  I'm loading it upright using the kayak cart hooked to the back of the SUV and then turning it over for transport so it's resting on the top side versus the bottom sitting on saddles.  When I slid it off the back onto the cart wheels to unload (like I did with the Trident 13), that "flow valve" catches on the racks.  Working on another easy single person car-top loading method.  I'll figure it out, it just seems funny to have the option to NOT let the cockpit drain...and yes, I realize the picture looks like a distasteful selfie

That's the hidden camera that Hobie uses to spy on it's customers.

LMAO!
I have pondered that same question on my Hobie