I have never seen BB connected with UNC in the past (he has certain schools/Coaches he has relationships with)
I'm sure there is more to it, has to be, like this probably means nothing but all I can connect right now is what you like heard about his dad being an assistant at NC a long long time ago which would have had young Bill living in the area a young kid, shown in this photo:
https://x.com/LeePaceTweet/status/1865044512109682914.
And there is this from Mike Sando:
Bill Belichick's late father, Steve, helped get Bill into the NFL thru his friend, George Boutselis, who in the 70s worked under
#colts coach Ted Marchibroda, who gave Bill his first job in the league.George Boutselis was a quarterback at UNC and coached there after Steve Belichick coached there.