Started by fixing the variables jenkinsBuild and jenkinsProject for pipeline builds (which also removes one deprecated method call at least). Then created a few pipeline jobs to test the plug-in. As expected, when you add "This build is parameterized", everything works as expected.
This doesn't match my experience — groovy.lang.Binding only has the jenkinsParameter variable for any pipeline job that I test, "This build is parameterized" option is checked on each one. Is this fix not included in the official releases yet? I'm using Active Choices plugin version 2.2.1