I haven't mentioned anything about grocks, I've been discussing a defenders ability to manage a ball that has been crossed into the box.
But, let's say that this played out, and we sold Stones next summer for £50mil. You'd want us to spend that money (or some of it, at least) on two defenders who by then would be 29 (Dann) and 28 (Shawcross), and not liable to improve.
While they might be able to defend crosses, they would certainly not be able to play it out from the back as Stones does, which is key to our style. So you say that being able to defend crosses would be the difference, but surely that difference would be negated by having two centre halves who are far from Stones' ability.
Also, Stones is not a bad defender, far from it. He tends to have a moment where he may switch off (e.g. Arsenal) but then again so does Jags and so do Shawcross and Dann. Would much rather have Stones in the side.
And, as a note, why would Stoke and Palace want to sell their two best defenders, and players that are ideally suited to their style?