Sorry you got caught up in my very wide net. There has never been a reason to flush a transmission other than to sell more transmission fluid. Vehicle manufacturers do not recommend transmission flushes as a whole. They do allow some flushing with certain machines and for certain procedures. Flushing transmissions as preventative maintenance is flawed logic.
Mechanics should always avoid the “potential” to do harm to a vehicle at all costs. Flushing is not 100% destructive and I know that. If done properly a transmission may not be damaged at all. On the other hand, why take the chance? That’s why a mechanic who advises a procedure that may do more harm than good is incompetent in my book. I’m sure the vast majority of mechanics will agree with me and I stand by my comments. I have personally seen friends and family shell out for new transmissions right after a transmission flush. I have never had a transmission failure and I have never had one flushed either.