As an early 90’s millennial, I’ve never noticed a “gen z stare” as described in news articles like a “blank face that shows lack of social skill or ability to think”. The only times I’ve witnessed it happen and seen the older person accuse them of “gen z stare” is when the older person says something off hand or dumb but isn’t self aware enough to realize they’re being weird. Hell, I’ve given people a blank face countless times because I was taught it was better to say nothing at all sometimes. Especially when it came to talking to older people at work.
I remember when I was 16, some middle aged guy at work accused me of having no personality. In reality, I kept all conversations short as possible with him (like almost everyone in the store) because they were casually racist and misogynistic.
a lot of people try as much as possible not to acknowledge the humanity of service workers, its completely normal for those workers to become numb to the endless stream of jackasses. Even if the next guy coming up does acknowledge them and treat them like a human, its hard to fault any perceived carelessness. Its also not limited to young people, any supermarket I go to has older peole working and you will encounter the same phenomenon. Its the alienation of labor under capitalism.