The advice is so wild in this category that in the 80s, before synthetic, I knew a "lifelong mechanic" who proselytized the virtue of never changing your oil.
His claim is that emptying the oil got rid of thicker particulates that kept the seals healthy, so no flushing/changing should be done.
"Keep changing your filter everyone in a while, and just keep adding new oil"
No, it wasn't AmsOil or some other crazy stuff.
People are out of their minds.
Car manufacturers want you to replace your vehicle sooner - you can see it yourself with Ford doing the 3-bolt diff, they do not care about you.
Do the math. Oil every 10k miles means you only change the oil 3 times before your warranty is up. 10 times if you get one to 100k miles. Why would they do it if it costs them money? It doesn't - they charge $200 for a full-synth oil change.
Everyone will do what they want, of course.