The answer, as we know, is that another way to establish what nationality someone is (or at least what nationality predominates) is to do a DNA test.
I'd gathered that Jews are not actually allowed to have such a test if they're living in Palestine (stopped by the Government from doing so). Though nothing to try and stop them from doing so if they visit another country (ie combine having a holiday in another country and do that verboten DNA test whilst they're there) and get the result telling them what nationality they are before they go back there (ie if, for some reason, they don't know what nationality their parents are). That's possible, I guess, as I don't actually know what nationality my mothers father is (as I was told her grandfather was her father - and so I assume my own maternal grandfather was English).
I struggle to get my head round their way of looking at nationality - as it's so different to everyone elses. The only Jewish person I know (and we're friends) describes herself as South African - because that is what she is and where she was born. So she says she's Jewish - but she is South African and lived there till she was 16 - prior to moving to Britain. She'd have no problem knowing which country to go back to if it came to it = South Africa.
Well yes....I guess it would create problems for a DNA test to come up with a result of, for instance, "You're 70% Polish" and that would make Poland the obvious country for that particular person....