That’s the human equivalant of the “sir are you aware you are a cat” meme.
I thought I was Jewish when I was her age but I was actually Catholic so when my Jewish friends invited me to give a prayer at his house during Chanukah and I recited “Our Father who art in heaven…”, my friend’s mom got on her knees and said to my face in a super soft voice, “Joey, I think you’re catholic not Jewish,” in front of everyone and I thought I was in trouble and I started crying.