A paper in the Lancet in August 2021 from Oxford University and Wellcome indicated that vaccinated people were greater spreaders of virus than those unvaccinated (ref. google Data on breakthrough SARS-CoV-2 Delta variant infections Vietnam).
Since the vaccination neither prevents transmission or stops it why should anyone be concerned as to someones vaccination record. As reactions to vaccinations have apparently or allegedly occurred it may be the unvaccinated who could be at more concern over needing to take control during flight.