Grades are quite interesting from a philosophical point of view. An attempt to apply a relatively simple system of overall difficulty to something completely ahuman I.e not designed for that, or even designed at all.
I'd say tall people need to accept that tracksides is just easier for them and short light people just need to accept that ratty crimps on a limestone 40 degree overhang is easier for them. I suppose you could take it one step further; being tall is genetic, being small and light is genetic. Being good at pulling really hard on holds has a strong genetic element, as does finger strength, as does everything really. Would someone say "easy for me I've got genetically talented fingers" or "hard for me cos I'm naturally not suited to climbing" they would not. Height and reach are areas we sort of accept that it is okay though cos you can literally do fuck all about it (whereas you can get stronger fingers even if genetically you might be predisposed towards weaker ones).
Anyway I think a consensus should arise based on what an "average" climber would be required to do. If you can lank the crux well done, it's easier for you and you know it, so long as you can sleep at night all is well.