Just want to share my recent observations on WHR accuracy with sensor hub 4.2. I commute to the office on bike, and since WHR was introduced (and I got the VAHR some years ago) I have not used a HR strap for the commutes (with the odd exception). Through the years I have had regular occasions with poor HR, especially in cold weather, with HR spiking up and above my max HR - or staying much too low. This would result in training loads way above (or below) reality. My commute typically gives a training effect of 2.0 (give or take) and 0 anaerobic training effect (or very low). Before upgrading to the 4.2 sensor hub I could see heart rates 20 to 30 beats too high, and aerobic training effects up towards 3.0 and anaerobic much above 2.
But since I installed the 4.2 sensor hub in the Beta 6.77 the HR reflects the efforts during the commute in a much more realistic manner. Especially in the current chilly weather. It remains for me to try out the WHR in other activities, like hiking/climbing (with poles), alpine skiing and in warmer weather than currently. But so far so good. Obviously I use a HR strap for all activities, with these exceptions.
I know there are complains over at the F6 forum, but for my use cases, I am seeing improvements.