I have heard it stated by some scholars that generations don’t exist, but cohorts do. That is, our bracketing of ranges of people into particular generations is artificial and bins what is truly a more continuous variable into a few categories. The same criticism applies to the Myers-Briggs typology in personality (the main reason psychologists prefer the “Big Five”).
But the flip side of this issue is that to talk reasonably about some phenomenon you have to bin and categorize continuous variables. Human races may not have hard and fast boundaries, but human genetic variation is difficult to talk about unless you use some categorical shorthand.
Some of the same applies to the term immigrant and native-born. The reason I’m putting up this post is that there was a discussion online about whether there can be something called a “second generation immigrant.” That is, someone whose parents were born abroad, but they themselves were born in the country of their citizenship. Myself, I think the term immigrant should only apply to those who were born abroad. Native-born and immigrant are disjoint distributions.
But, there are more than a few categories here within the dichotomy. When you arrive in your life, and where you arrive, matters a great deal.