Depending on where one is located in the UK, maybe a smaller front sprocket or larger rear sprocket is the way to go on the pre-2023 models to allow the 1st gear a more usable torque, especially for take off in city traffic and head-wind conditions?
Yeah, the 6th gear will end up with a higher rpm for a set speed vs the stock gearing setup, but one has to weigh up how often one rides at those excessive highway speeds with all the speed control cameras in use.
Besides, the lower gearing has so many more advantages in slow moving traffic, lower torque when riding off the beaten track, a 6th gear lower gear ratio could make it not necessary to drop a gear or two to accelerate past some plonker holding you up or to simply move into a faster lane, etc ....
Have a look on
https://www.gearingcommander.com for info relevant to your model. Do remember that the info on gearingcommander is under ideal conditions plus on a level hard surface. So if one rides more in twisty or hiily country, then perhaps keep that in mind when looking for a better sprocket size.