a plugin's dependencies can influence other plugins in a build

See the linked issue for more details.

In short, the dependency plugin has declared a dependency on the site plugin (forget for now that this is probably not a good ide). The problem is that in doing this, the site plugin used for other things in the user's build is now pinned to the version declared in the dependency plugin. This seems to indicate some kind of pollution between what a plugin needs and what gets used for a build.