The purpose of this pronouncement by Stone is to make Cruz look even shiftier (if that’s possible).
Stone is broadcasting all of the available tricks that Cruz may try to pull to steal the nomination from Trump. He wants the voters and surrogates to know what is possible.
Cruz is meeting right now with the committee and I’m sure Stone knows people on that committee who will let him know what transpires.
Cruz doesn’t need Roger to make him look shifty, he’s quite capable on his own. Both men are equally slick, except that Stone never pretended to wear a halo. Cruz makes Stone look good.