I think your question is highlighting a difference in readily available learning material via the Internet that younger generations take for granted. "Self-taught" traditionally conveys a lack of formal education, specifically college-level. Otherwise, a school, degree, or both could be shared.
As the school or degree is shared as a credential, the "self-taught" clarifies there's no need to dig further for this credential.
There is just SO much knowledge available now that I didn't have when I was younger, much of it rivaling anything you can get in a school. I would think that maybe 20+ years ago saying you are "self taught" would be a flex but really doesn't feel like it now
It was never meant as a flex. Someone would be digging for creds that you didn't have, and you'd say that up front to avoid the dig. As far as available knowledge, I've ALWAYS heard that networking is the biggest benefit of formal art education. Past or present, you've got to practice to get good.