I haven't had a 10 speed only hub... but they are pretty rare. They came out briefly (like a year or two, and then reverted back to the old style.

I think it was basically abandoned once 105 moved to 10 speed, as it was a Dura-Ace/Ultegra 10 speed thing... I seem to remember reading on Sheldon Brown's site about how to file non-DA cassettes for use on DA wheels...

I am surprised the two LBSes didn't catch it either, so I am surprised that this is what you have.