The Netherlands international profited from a Diego Gonzalez error to give Barca a 39th-minute lead and crossed for substitute Riqui Puig to score a late second in Sunday's LaLiga clash.
De Jong now has three goals and two assists in his last six games in all competitions, while his five LaLiga goals in 18 months at Camp Nou is one more than he managed in five seasons in the Eredivisie.
He also contested more duels (11) than any other Barca player at Estadio Martinez Valero and no visiting player intercepted the ball more often (twice).
But it is the attacking side of De Jong's game that most pleased head coach Koeman, who wants his midfielders to take the goalscoring burden off the forward line.
"The three forwards aren't enough; we need the midfielders to score too," Koeman said. "It's good that he's scoring and assisting.