Yoga and HRM-Run

Hello everybody,

I am using HRM-Run during morning set of exercises:  Run, then Strength and finally Yoga. During Run and Strength sessions wrist HR LEDs are out. This is expected. However, during Yoga LEDs are shining despite the fact HRM-Run is still on me. Is this a feature or a bug? Where from the HR readings come when I write my Yoga exercise?

(q6, 13:10)