I know, but you must also know that there is some animosity from NC State grads toward that UNC pull and dominance. Note that the UNC academic scandal has gotten a lot of press despite the NCAA cover up due to investigations by NC State grads. UNC will not exacerbate that animosity by blocking NC State from something that is clearly beneficial for NC State and the state of North Carolina. Again, just my read of the politics, I appreciate that UNC would try to discourage NC State from leaving the ACC, but when push comes to shove, if NC State sticks to its guns I don't think the state will block them.
That assumes NC State can get an offer. It's possible neither the B1G nor SEC will offer State as long as they think UNC might come to them, so there may be a stalemate.