No Im not believing internet urban legends Im going from experience. But Im not going to argue with you unless directly responded to. I dont have transmission problems personally but I have seen the flush machines ruin cars and trucks from being flushed by them.
Also Im at 330,000 miles on the factory transmission in my truck, 280,000 miles on my automatic bmw, 245,0000 (I think) on my wifes automatic bmw to list a few. No failures so far following what I listed and no flush machines either.
Ive seen way to many cars and trucks screw up after being flushed to take it as random chance.
I look at the flush process being needed to "fully" change the fluid about like that internet wiz recommending changing the oil in the hpop rez
A normal fluid and filter change gets enough out to handle the jobs.