I would agree with you in when they ask where you’re from. Once they start asking where your parents and grandparents are from they’re trying to figure out your race.
I also agree with you as a white guy I don’t usually get extra probing but there are a few, mostly older, that are trying to figure out what specific type of white. It occasionally ends with a comment about how some group isn’t really white even though they have light skin.
I would like to know more