You'd think this was true, but I've seen some crazy shit in interviews, even at companies that were big enough and had a robust enough legal team, where you'd think they'd have their shit together.
I once interviewed at a medium sized, name brand Silicon Valley darling everyone on HN has heard of, where an interviewer outright asked me if I was married and if I had kids! Like, holy shit, just read your interview training manual! The very first sentence is probably "Do not ask any questions where the answer would even imply information about things that would get us in trouble discrimination-wise." Yet this person overtly asked! Here I was in the stairwell walking down to the second floor and she hits me up with one of the few totally forbidden questions! I thought about saying "What would HR think of that question?" but the asker was the HR manager! Totally bonkers.
The way I understand it, you can legally ask the questions, you just can't consider protected status for hiring purposes. The interview guidelines prohibit asking because "we didn't ask" is a stronger defense than "our interviewers have mental firewalls".
This case is strictly worse because the questions are explicitly being asked to evaluate eligibility for hiring.
It's still a major blunder by an HR manager but maybe there's a chance that they had already decided to hire the person but hadn't made an official offer and it was a mistimed getting-to-know-you chat? I don't know, it seems insane to even ask.
My wife was asked that question ("are you married, do you have kids?") in an interview with a tiny company 30 years ago. She attributed it to ignorance and replied "That's not a legal question to ask". The interviewer apologized profusely and he hired her. He turned out to be a really nice person who was unaware of what was out-of-bounds to ask in an interview. But that was 30 years ago, people should know better now.
I once interviewed at a medium sized, name brand Silicon Valley darling everyone on HN has heard of, where an interviewer outright asked me if I was married and if I had kids! Like, holy shit, just read your interview training manual! The very first sentence is probably "Do not ask any questions where the answer would even imply information about things that would get us in trouble discrimination-wise." Yet this person overtly asked! Here I was in the stairwell walking down to the second floor and she hits me up with one of the few totally forbidden questions! I thought about saying "What would HR think of that question?" but the asker was the HR manager! Totally bonkers.