Not just failed transmissions but zero symptoms from not following those instructions. There would be noise, shifting, codes, or other symptoms…if it was an issue.
But quite literally none - not one person in 10 years has done just a drain and fill and had issues. And I guarantee it’s been done tons of times. I mean look at how many CVTs fail.
It’s not definitive but highly suspicious. In 10 more years we will probably find out it didn’t matter.