It's not just idiocy IMO. I've ridden a Pactimo summit jersey on my last few RAMRODs and yes, it did seem better especially than my usual not-skin-tight jerseys in the heat. Makes sense. It can't get rid of heat unless it touches one's skin and is made from a high moisture transfer fabric. 26% does seem a bit high. OTOH I've ridden past folks who had to stop and cool off in the shade. As it is said, there's no lower speed than stopped.