Does HealthKit data lose fidelity over time?

I'm building something that includes functionality that allows a user to import a HealthKit workout and any associated heart rate samples. I've noticed that workouts that happened in the last 60 days or so (I don't know if it's a hard date cutoff) have what appears to be a full stream of heart rate samples. After that, the resolution of the heart rate sample data drops significantly. We go from having somewhere around ~500 heart rate samples to about 10 for an hour-long workout. I've confirmed with several other people that this is also happening to their data by asking them to go into their Health app to look at the heart rate samples for workouts that occurred a few months ago.

This issue is verifiable without writing any code, so I feel comfortable that the problem isn't with how I've implemented HealthKit queries in my code.

Is this expected behavior from HealthKit?
Does HealthKit data lose fidelity over time?
 
 
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