My (somewhat educated) guess is that questions like this are asked not just about the content, but to see how the person reacts to the questions. Someone who's been put on (and not a professional liar or psychopath) without knowing the applicant will do certain 'tells' that they're lying (like making up obvious nonsense or getting very nervous instead of saying 'I don't know.') Does it matter you know if your friend is Italian? Probably not, but how you handle not knowing might.
And keep in mind individual questions (like height) may not matter much, but cumulatively could. Answering things you probably wouldn't know - exact height and weight of somebody you don't know that well - would possibly also finger as a fake.