Display forwarding - for non-X programs?
As you say the answer is no. OSX does not include a remote graphics display whilst X11 does. (The Cocoa API is based on the NeXTStep API which was drawn by Display  Postscript which allowed remote graphics display - however the license cost too much for Apple to use)

However this is a general answer for all applications. But you can configure matplotlib to use an X11 backend and this can be displayed remotely. See this StackOverflow question.