Stress Accuracy?

I have a job where I am moving a lot, all day. My watch has told me since I got it that I'm in the 80-90 stress range all the time. Garmin Stress is related to HRV it seems mostly.

I have found with other wearable that they only measure HRV when you're sitting still and won't take a measurement otherwise. 

How can garmin accurately measure that if I am constantly moving all day?

For example, the Garmin HRV Stress activity forces you to sit still to get an accurate stress measurement via HRV. 

Everywhere I read it says to sit down and dont move to get an accurate reading.

https://help.welltory.com/en/articles/3361520-how-to-take-accurate-heart-rate-variability-measurements

https://elitehrv.com/the-8-biggest-mistakes-made-when-measuring-hrv

and more...