It’s definitely sad, not irrelevant because his sister has children, who probably now know they’re Jewish and we don’t know what the future holds for them or their (Halachically Jewish) offspring.
However, I have a strong suspicion that O’Connor knew all along. He knew that his mother converted but thought she was Lutheran prior? For someone so into religious teachings I find it hard to believe that he never researched his “roots” or questioned his mother about her conversion.