If you read the article, it basically says that many visits are actually the result of false positives. Listen to me. Going to the doctor after getting a false positive is still better than NOT knowing about the condition, right? It basically also gives alerts about abnormal heart rhythms, not just AFiB. Many users had a high heart rate during the recent presidential debate, so they also received a warning. I would say that it is quite accurate IMO, and that it is not a false positive nor an exception in your heart.