Not really, it does seem quite unreal but someone is naturally low on heart rate. However, this doesn't necessarily saying he is a great performance rider, because he can have a lower heart rate limit as well. Myself is naturally high but I also have a higher sustainable limit at 195bpm for which I can hold for nearly 20 mins on the hill. Though 170BPM is usually what I can sustain for a long ride that last nearly 6 hours. Plus you can obviously see, he is in a much stronger group than usual.