As funny as that is, they're wrong if the CWS record book is any indication. Maine did get only one hit on June 5, 1983 but Alabama pitchers also one-hit Arizona State batters in that same CWS-- on June 10th.
Looks like that was the last time a pitcher threw a one-hitter- when they put up that graphic the starter was still in the game. The other would be a combined one-hitter.