hyarr, seems like it be a bit of black magic thar, a sail popping out of the rigging? t'aint natural if ye ask me.
but on a serious note, sail shape is ruined when you furl the main around a boom, where as point reefing is designed and shaped with the reefing points in mind so sail shape is kept much better...or so i've been led to believe (you may have noticed by now i am a racer /forums/images/graemlins/blush.gif)
and you can lead the water down from the gooseneck into the tank.
It's interesting that in boom furling doesn't ever seen to have taken off, even though at 1st sight it's a simpler system than the more popular in-mast furling.
It probably has to do with the very high loads on a boom.
In-boom furling is used to good effect on the superyacht . Trouble with fit to modern AWB is that the boom is too close to peoples heads in the cockpit, and the in-boom system makes the boom even lower and heavier, thus even more dangerous.