On Windows at least you can uninstall using the Control Panel -> Programs -> Uninstall a program, all the NI stuff is listed there to uninstall.When they say uninstall, I don't think that can be done from within native access. They mean just going through your various folders and deleting plugins manually.
A bigger issue for me was how to activate plugins that you might already have installed and that doesn't seem to be possible either from Native Access.
I had all of my NI plugins on an external drive and the only options available in native access was reinstall, so that's what I did. I downloaded the entire Komplete for the second time in a few weeks. Lucky for me that I have fairly decent internet.