To wonder why people make comments such as just out of his/her 20’s

[Hihello7]

Saw this written about a 31 year Aibu to think 30’s is 30’s and 20’s is 20’s

It’s to emphasise the youngness of them.

Either patronisingly “what do they know, they’re just out of their 20s!”
Or to excuse them “oh let them off, they’re just out of their 20s!”