Not all ball joints make noise or have any symptoms of being bad, other then being loose. I see it all day. Rear shocks can leak fluid and still not be "bouncy". And belts that have surface cracks don't squeel.
Let me quote you "unless you have specifically noticed an issue with that system" Are you crazy? These flushes are to PREVENT problems with the system. Flushes are not to FIX any problem. That's just a dumb statement.