The legal concept you're referring to is called "ius soli". The legal concept which serves as a basis to determine someone's allegiance by their ancestry is called "ius sanguinis". [1][2]

[1] https://en.wikipedia.org/wiki/Jus_soli [2] https://en.wikipedia.org/wiki/Jus_sanguinis

So, no, it's not "common sense" to make that assumption.

Moreover, there's also the concept of "right to return" in international law. Many nations have implemented this in their nationality laws in a way that extends surprisingly far.

For instance, if you're of Luxembourgish descent through the male line of your family, you could just claim Luxembourg citizenship - and by extension E.U. citizenship - under Article 7 of their nationality laws. Something which was recently pointed out on Reddit. Even if you weren't born in Luxembourg or never have set a foot in the E.U. proper. [3]

[3] https://www.reddit.com/r/YouShouldKnow/comments/izkwzk/ysk_t...

I'm pretty sure some people might be surprised to discover they have a right to citizenship in another nation simply because they took the time to dig into their ancestry, their history and nationality laws.

> Interning people based on predicting their behavior due to ancestry is a whole different ballgame.

Of course it is.

But, why discuss someone's citizenship or ancestry then if it - apparently - doesn't matter in this discussion at all?

The only other theory that explains why this person got his access revoked from Github because he visited Iran, regardless of the reasons why, nevermind his citizenship or his ancestry.

If citizenship and/or ancestry matters, as is seemingly implied but never voiced in this discussion, then bringing up the implications of how policies reflect on that assumption clearly is relevant given the historic perspective.