I wondered why --skip-systemctl-redirect wasn't documented in the man_page for pg_ctlcluster?
I discovered it trying to figure out why running pg_ctlcluster from Saltstack on Ubuntu 16.04 was hanging - adding that flag resolved the issue. One of the first places I checked when running into the issue was the pg_ctlcluster man page, so I think it would be a good idea to add there...
Best wishes,
--
Casey