Holden = GM of Australia. What GM model is platform-related to any VW-group platform? It makes total sense that Passat (VW), Audi, and Skoda would share parts since they have been part of the VW group for a few decades. The Passat has flipped between being platform-related to Audi (lengthwise engine) and VW (transverse engine) several times but in either case the vehicle's design origins still lie within the VW group. But I can't think offhand of any GM model that might have been sold as a Holden which is platform-related to anything VW makes.
It isn't normal for a bodyshell part to be exactly shared between unrelated manufacturers unless it's part of a built-under-license or contract agreement of some sort or if the two vehicles share design origins (which still means there was a contract in place at some point in time). VW will own all the stamping dies used for producing parts for any VW-group vehicle, and GM will own all the stamping dies used for producing parts for any GM vehicle. Even if they're both coming out of the same third-party stamping plant - the vehicle manufacturer still owns the actual tooling, and unless there's a licensing agreement, it ain't being used for producing someone else's parts.
Back to the topic at hand - the Mercedes X-class and the next-gen (past what we've got) Nissan Frontier are shared designs which were built in the same assembly plant and differing only in decoration and, apparently, powertrains. It's pretty obvious from looking at them that the doors, windows, and cab are the same.