I took a look a look at the link provided by Toolman and it was interesting see that there is some empirical evidence for catch and release mortality to be somewhat offset by reduced angler success. That said, there are a couple of things that the numbers didn’t touch on that still give me pause - the first is that it seems that there is an assumption that angling (for trout) is always going to be less successful when the water is warmer. Thats probably fair in general, but exceptions are possible. The second is that it doesn’t touch on which fish are most adversely affected - if it’s anything like winter and/or summer kill events, it will be the larger fish that suffer the most.
At the end of the day, it’s hard for a one size fits all rule like this to be meaningful and/or effective over such a large and diverse area as the one it’s being applied to. That said, I read a quote once (and I may be paraphrasing) that said “a true sportsman does more than is required and takes less than they are entitled to”.