Your son made the right choice (saying this as a former UNC parent). Why be a guinea pig for an as yet undefined re-vamping of a department, when he can be treated like a king at Alabama (and go for free).
Aside from the Morehead Cain Scholars, the general attitude from UNC has typically been more of a “You’re lucky you got in” vs. “We’re very excited to have you here”. With my younger D going through the process this year, we are adding more weight to colleges that show excitement and make attempts to “woo” her into accepting admission. Go where you’re truly wanted!
I can also attest to the off-campus living at UNC being sky high (even 4 years ago when my oldest was there). I keep telling my husband that paying OOS for my younger D won’t end up being that much more than what we paid in-state at UNC when taking into account the cost of off-campus living, parking, eating, etc.