I reached out to experts for clarification regarding elevated HRV + depressed rHR.
HRV4Training: Daniel Rowland & Marco Altini
Any large deviation from the normal range, even in the “right” direction, but happening acutely is not necessarily something good. We see a similar impact for some users when they see a particularly high HRV score after a race or big training effort; in this case it is often a large parasympathetic response as the body tries to cope with the stressors it faced. …In periods of extreme duress, if you’re seeing any changes in HR or HRV where they fall outside the normal range, then it’s most likely a sign that you need to reduce the load.
Andrew Flatt Ph.D.
Was this increase in HRV observed during intensive endurance training? If so, you may have been experiencing the parasympathetic form of overreaching. This is well documented. We even wrote a meta analysis on this.