And they are correct according to the meaning of the word. Expats simply means someone who resides outside of their native country.

I guess colloquially it probably implies moving somewhere as an adult, but the word itself doesn't carry that meaning (it's literally ex=outside + patris=homeland). But for instance, my sister has lived permanently in New Zealand for 25 years now (and a few years prior to her permanent move) and has no intention to ever leave, but would still be considered an expat. Her children were born in the UK, but they were 4 and 2 when they moved there, and I don't think they'd ever have considered themselves expats as they've never known anywhere but NZ. In fact the oldest is visiting the UK for a week this year, it'll be the second time he's been in the UK since moving to NZ aged 4.

That is the original definition, but then all immigrants are expats, and all expats are migrants. The words become synonyms. Then its become very interesting to ask why people prefer one word over the other for particular groups of people.

To me, it's useful because it frames it in terms of social connections in the target country and because how it works with an adjective.

So, British expats in Spain and Chinese expats in Spain are likely to socialise in their specific group, but rarely if ever intersect. They are all immigrants in the target country (and especially when considered as a whole as everyone from "outside"), and they are all expats (but probably in defined cliques).

I'd say these clusters of people are living the "expat life", but equally there are many immigrants who don't particularly want to hang out with other expats, because they're not trying to recreate where they left in a new place, but are trying to assimilate to the new place. They themselves are still expats even if they don't socialise much with other expats, but wouldn't be living the expat life.