Well yes. Marv is correct here. As with the case of Aleix Vidal too. The player is contracted to the club but can't be registered in the teams for the various competitions. I know Enrique likes to rotate sometimes but I don't think it's a good move for Arda.
Anyway Barcelona have reserved the right to re-sell Arda back at the same terms till July 20th. The new president will be elected on the 18th. If it's Laporta he might very well do that and try and sign Pogba.