Yes it is, made on July 17 2016. Just checked ZTL myself and indeed Duisburg is not mentioned as a current holder. If you look at the Kori bustard ( no subspecific status ) former holdings at Duisburg it's mentioned "aktuell nur noch Tiere der UA struthiunculus im Bestand, vormals auch der Nominatform (siehe dort)" = actual only animals of the subspecies struthiunculus kept, formely also animals of the nominate-form !? In the section of the Northern sub-species Duisburg is however not mentioned.
But I've seen them myself as the photo proofes so at least in 2016 the species was still at Duisburg !
For me Duisburg is listed on ZTL as a holder of both the Southern and the Northern subspecies of Kori bustard, as has been the case for as long as I know.
