I believe the temperatures within the chart are “feels like” temperatures rather than absolute temperatures. The X axis shows absolute values (what would likely show on the thermostat).
At OPs original temperature (91°F) the danger zone would be around 60-70% and higher. At OPs last updated temperature (94°F), the danger zone would be 55% or higher.
Lots of things cause harm while also doing good things. It’s a balance.
The problem is when that balance skews more one way than another.