Follow the incentive: who benefits from this simplification of the impact of humidity?
The idea that thermal comfort is a simple property of climate offers an easy classification, but ignores local adaptations.
The economic drivers behind such guides encourage simple narratives, but in Luxembourg, we see that solutions like air conditioning transform the experience, making a "humid" region perfectly tolerable.
A traveler in a fully air-conditioned hotel in Dubai during summer will not experience the same discomfort as a camper in the Amazon rainforest, even with similar raw humidity data, because infrastructures change everything.