Another bug? HRM-Run and RUN activity. Watch HR sensor LEDs still working

As subject says, yesterday I made a run activity (firmware 2.50) with my hrmrun4 band. What I've noticed is that while strap was working as I was getting power data fields and advanced dynamics I've also noticed that FR945 LEDs were blinking all the duration of the workout.

Is it not supposed to be OFF while using hrm-run?

(I can confirm that on Fenix5 leds are OFF).