"Obviously Oprah had to ask something during the taping, but agreed beforehand she wouldn't be too hard on [Rob and Kristen] if they told her what was really going on. Both Rob and Kristen's people and Summit then confirmed ahead of time [Rob and Kristen] are together and are dating. One hundred percent."
At least O knows how to get it out of them somehow! And really, are you going to lie to Oprah? No way!
So that's the little agreement our fave couple settled on. They could get away with the deflected joking answer, but Oprah (and her crew) needed to know what was really up with them.