No, it has nothing in to do with NeXTSTEP. XPC was designed recently and for macOS/iOS. This is just that it was not designed with security in mind along this axis.
That is the thing, the OS architecture wasn't revamped across the board, XPC became another little island how to do IPC.
XPC has been in shipping platforms for more than 13 years... I suppose that is recent compared to NEXTstep :)