Exactly that. Most people have no idea how the stance position/setback relates to the sidecut (as opposed to just the position along the length of the board). An SL does not become a true twin simply by slapping the bindings on the board without setback.
Don't even get me started on flex...
It needs confirmation from Vman/Vince or NS themselves, but an older post had the author saying they actually contacted NS, and they said if you adjust it, it is a twin.
Then again, it's a 1/2" setback. Who's going to really notice that.
SL describes it as a twin shape. that would mean the sidecut as well. It's best to contact NS, but again, who would notice a 1/2" setback. If you are good enough to notice it, you're good enough to ride it too IMO.