I installed ‘Cumulative update for 21H1’ (not 20H2), KB5003173 last night after which, with no settings change, I resumed my southern France bush trip in VR. Prior to the update I was averaging around 35 FPS so I was surprised and disappointed to see I was only achieving 30-31 FPS after the update.
Too early to be sure that KB5003173 is the reason for the lower FPS but I will be very interested to see if others have a similar experience.