Back in my FK8 days (aka last week) I found a very handy material to stuff into joints to add some pressure and stop creaks/rattles.
A Kleenex folded onto itself into a puffy square. As long you don't see it in your line of sight it's a perfect quick fix.
From what I understood he isn’t saying each engine is run for 3 hours and then tested in the production lines.
When they are benchmarking the engine design before release they do that to make sure the process is good and all is well.