I have had consistently inconsistent results with recreational modules.
When I put them in as part of a megaton-sized set-it-and-forget-it orbital station like a fuel harvester or massive asteroid mining platform, they work as advertised—that ship and ships near it don't run up deployment time.
When I build a small dedicated recreation ship—just the rec module, engines and fuel to push it, and crew quarters to run it—and send it out with fleets of smaller mobile miners, oftentimes they
don't work: the recreation ship itself still runs up its deployment clock when away from populations and does nothing for other ships. Sometimes they
do work, though. When they do work they work great; when added to a task group a working recreation ship keeps all deployment clocks frozen at zero even in transit between system bodies.
I cannot for the life of me figure out what 'activates' them.