There’s not really any substitutions allowed with the woot offers. If you want a full case of the Cab, and only the Cab, you’ll have to buy it directly from the winery. The winery may grant some kind of a woot discount for people who purchase this offer (it happens, occasionally), but in general, on wine.woot, what you see is what you get.
These offers are specially crafted to be given at these prices. This is, however, a great way to branch out with the winery if all you’ve had from them has been the Cab - get a sample of more of what they make. Who knows, maybe you’ll find a new favorite from them!