Today I went out and ran a 10 miler attempting to duplicate this his slow pace (11:20 overall pace) and keep my heart rate low. I also wanted to attempt to "cheat" by taking my Coros
off and putting it back on at two mile intervals. In my opinion the only way he may be cheating is by passing the watch from person to person. This would also explain the heart rate anomalies with fresher runners taking over shifts.
When I took the watch off it did not mess up the data at all. The only time it dropped pace completely was when I had the watch off for a full 30 seconds. But here is the kicker. The drop in data blip only occurred on Coros web portal. When it uploaded to Strava the data seems to "smooth" so you could see nothing abnormal about the entire run. The times I took the watch off during walking showed nothing abnormal. Pace, cadence and heart rate all look typical for the run/walk.
My conclusion: If you had someone walking or jogging with you as they took over your running shift, you could easily pass the watch over in about 10 seconds max. It would go without detection as you reviewed the day's running data.
I did not have a chance to test it with a 2nd runner yet. Perhaps someone else could try that out. In other words, does the data look much different after it goes on the wrist of another runner trying to run the same pace and cadence?