Well, it's quite possible that there is not one common understanding what a useful RHR computation method is, but whatever method we (or Garmin) choose it is important to be consistent and stick to it. Trying to do it in varying conditions will likely give us not very meaningful results.
Anyway, I can understand your line of thinking. However when comparing to the intelligent method of determining LTHR we must take into account that LTHR computation is done by Firstbeat algorithms, made by a company who specializes in that kind of things, whereas RHR is calculated by a extremely simple rule, probably implmented by Garmin.
Simple just stop the main activity session to get a reliable RHR value while standing still for 2 mins. Then add a separate warm down session which isn’t as important as the values of the main activity session where all your important metrics & data will exist..
A heart rate recovery trend graph would be very helpful. At present I have to hold a general trend in my head by remembering a succession of RHR values after my activities then I can tell if I am getting fitter or not as the HR reduction number goes up!
But it would be great to see a history graph akin to ‘heart rate variability’ graphs which is also crucial to preventing over training.
I know generally speaking if my heart rate recovery value is under 60 then I am over fatigued, if my heart rate after 2 mins has come down more than half that of the total maximum heart rate at the end of a workout I know I am really race ready. Example MAX HR- 159 RHR-74/85
