Doctors will rarely subject anyone to thorough evaluation for things if they aren't over the common danger age and don't report specific symptoms. Your typical annual checkup for people not 50+ is a fairly generic blood panel and very little else. After 50 they may add, what, a prostate probe for men?
I see a large part of a doctor’s job as being an expert consultant for an individual to make decisions about their own healthcare. Someone who is interested in and involved in their own risks is likely an extreme outlier to begin with.
In my life I've had one doctor who performed an EKG as part of my annual checkup, once.
The other ~10 primary care physicians I've had never did -- my annual was mostly just a few questions, some blood work, quick reflex tests and I think they looked in my ears and eyes.
If my Apple Watch detected a heart irregularity, I can say with certainty it's not something that would be caught otherwise at my next annual checkup.