The dnf repoquery plugin is missing the "--installed" option which the repoquery command had, which would limit the results to just the packages which the system already has installed.
This is implemented from dnf-plugins-core-0.1.6-3 and it is "--installonly" in dnf's repoquery.
--installonly is used to select packages which are never upgraded, but only ever installed, like kernel packages. "dnf repoquery --installonly '*'" lists the three kernel packages installed on my computer, for instance. Replacing "*" with any other installed package lists nothing, since those packages aren't install only.
*** This bug has been marked as a duplicate of bug 1199601 ***