To me, the biggest problem with giving frozen or cold treats is that some people apparently think that this cools a chicken down. Inasmuch as it does cool a chicken down, the cooling effect lasts a very short period.
Restated, I suggest frozen or cold treats should not be part of the plan to prevent chicken heat stroke and death.
In an emergency, for an overheated bird, certainly a cold treat would be reasonable. But in this regard, the cold treat is actually treatment for a condition that we were earlier attempting to avoid.
Many threads start with "How do I keep my birds cool" followed by people listing cold treats as one of the top things to do. From my perspective, chickens in the summer heat are like construction workers on a very hot job site. If its my job to keep them alive, handing them a popsicle every hour just isn't appropriate. I would feel like I was doing something, the workers would appreciate the popsicles, but the popsicles won't prevent heat stroke.