I wouldn’t say definitively that every mushroom is safe to chew and spit out. There could be some toxins you’d absorb through the membranes of the mouth. I don’t know of any but there are a lot of species of fungus. Maybe fire coral mushroom?

There is also Gyromitra which can be rendered mostly edible by boiling… however, the toxin is volatile and can be inhaled by the cook causing poisoning through a fairly unique mechanism.