I am very aware of what the watch does. A doctor is not going to diagnose atrial fibrillation based on a single ECG lead. They are going to do a more complete ECG (either in-office, or with a Holter monitor style device at home).
The watch absolutely plays an important role (it's a widely distributed, high SNR screening tool; that's definitely valuable), but it's not replacing more complete diagnostic tests.
As a meta comment... I think it's good to avoid using "you" too much when replying to someone. Respond to what someone said, not assumptions about who they are, what they know, or what their motivations are. For whatever it's worth, I am a software developer and paramedic.
