Apparently the Gerrit Trigger plugin only recognizes the value if it matches specific pattern. Therefore there must be "gerrit version 2.16.7" so we can use all features of the plugin.
Ferrit is a Fake Gerrit server implementation created for functional testing of events in Jenkins & Gerrit Trigger ecosystem.
TODO
Ferrite image by Karl-Martin Skontorp is on Attribution 2.0 Generic (CC BY 2.0) license.