So is this chart saying that pretty much everything they tried made the core hotter?
I interpret it as:
In this study, this is the stuff they did and see what happens to core temp. These types of things do not reliably change the core temp at all. This was just to be used as an example that very cold things like ice cubes placed on the body for short periods of time do not change core temp much at all. It has to do with surface area/physics etc. Even hand/forearm immersion is not enough to change it much and palm cooling appears useless.
I know iced towels/cooling blankets work, as we use them in the hospital. I know cold immersion works as it is a treatment for heat stroke.
How much evaporation you get or conductive cooling with cold water during a hot triathlon? Questionable there is any significant relief. Although, I do believe that even helping for 5 seconds can help your brain believe that you are feeling a bit better. But, that is an opinion only...