I think he means that in the family heirachy he's still the uncle so even his niece dates older he's still higher up in the family tree.
If you count his niece as her friend then yes, but if you count her as his journalist then no. He might be older than her a few years but not a generation. What he meant there if his niece date Shuyi's friend then he will be one generation younger than him because that his his hierarchy with his niece.
I don’t know if they gave their ages at some point but it makes it feel like his niece is in her early 20s, FL in late 20s/early 30s and him is late 30s, so even if his niece dated a guy 10 years older, he would still be almost 10 year older than him.
No lol, that is just how hierarchy work in Chinese because I'm Chinese. The age is not like that. His niece is in her 20s, they (fl, ml, fl's friend) are in their 30s
So his older by a generation than her?