@arstechnica
Morchella are edible mushrooms that need to be heated before eating, wikipedia says so in at least three languages with sources. There is no mystery.
No need to expand one groups toxicity to others - button mushroom being prime example of delicious whike non cooked.
There are ofcourse others, and there are of course caveats.
Tho the say they haven't found a definitive cause for outbreak when I read that the morels at the sushi restaurant were either raw or lightly cooked, I remembered mycologist Paul Stamets advising to always thoroughly cook fungi.