The authors of the cited article refer to the toelrability thresholds in this sentence:

"In controlled experiments, critical wet-bulb temperatures ranged from 25°C to 28°C in hot-dry environments and from 30°C to 31°C in warm-humid environments."

I think that there may be confusion between what the temperature "feels" like given high humidity, which ties into comfort level, and what is actually dangerous.

My understanding is that when it is dry people dehydrate much more rapidly, and that dehydration interferes in multiple ways with the ability of cells and organs to function.