Apparently, there is a trend towards calling anyone you don't know as uncle or auntie, and it is considered an insult.

Men and women in their 20s calling men and women in their 30s and 40s uncle and auntie.

This is correlating with the boomer insult word towards anyone older than you and it's being used by salesmen and women in malls.

If you're in your late 20s or early 30s and then an early 20s adult calls you auntie or uncle, would you consider it offensive?

Nowadays these terms are used as a pejorative towards those you dislike and are older than you even though not much older.