To say this win, at Carter, was not an upset is a bit of a stretch.
While Stone has indeed played the teams you cite, they lost almost every one of those games.
That said, they are also an obviously improved team over the first part of their season, winning 12 of their last 13 games (including an impressive 84-67 win over Alcoa in late January).
Basketball is a tournament sport, and Stone is certainly on a run at the right time.