Pianists with large hands currently have an unfair advantage!
Nobody suggests that adjusting stool height or installing raised pedals is unfair, or that prominent pianists who use, or have used, smaller keyboards (such as Josef Hofmann 100 years ago or Daniel Barenboim today), are ‘cheating’, or that Beethoven was ‘cheating’ because he played a keyboard that was smaller than today’s conventional size!
Until narrower keyboards become more widespread in the community, then those pianists with smaller hands will be disadvantaged compared with others who do have access, but as more and more pianists get to try keyboards with narrow keys and become aware of the barriers they have faced all their lives, they will eventually generate the momentum to force change by the manufacturers.
If piano playing were a purely physical competition, like running a marathon, then the aim would be to find out who can play the most notes in the shortest possible time!
Piano playing is an art, not a sport. Most other musical instruments have more than one size available to suit the diversity of human physical characteristics.
Even for many sports, runners are not expected to run in the same size shoes, or skiers use the same size skis!