I doubt that that's the case, as it would have to have a USB hub built into it. But I suppose it's possible. Just remember that it'll have to have some intelligent circuitry in it. If someone tries to sell you a simple Y-cable, I imagine that he'll also have a bridge to sell you.

Honestly, I looked around for a while yesterday, and I couldn't find a single USB product that had mobo-style USB headers on it beyond an actual motherboard.