I'm willing to bet that's mostly urban legend. Anecdotally speaking, I have extended family who use Apple products and who text our Android-using family.

It's a thing, but largely limited to teenagers. It's a great way to show you're cool and part of the in-crowd and to shun "the poors."

We were told by a cousin of a friend who was in their first year of college, so that checks out

It's a thing with adults, too. People bring it up at work about the texting they do with other employees. It's obnoxious

It’s real but it’s real at the level of people who wouldn’t let you hang out with them if you didn’t have the right brand of shoes or looked down on you for not having a BMW/Lexus. RCS support in iOS 18 will get rid of the only legitimate concern but I’m betting those people will either continue unchanged or pick a different signifier. Your life is always better off without people like that.