mushrooms are not fruit, nor are they vegetables.  In fact, mushrooms aren't even plants---they belong to the fungus kingdom.  Genetically speaking, they are more closely related to animals than fruits or vegetables. 

It's dangerous to pick wild mushrooms unless you have a mushroom  encyclopaedia to hand before eating them. Some poisonous mushrooms can kill you - for example, the deathcap mushroom doesn't show symptoms after consumption until c.2-3 days later, by which time you suddenly need a liver-/kidney transplant or you're dead - and it's easily confused with the common field mushroom which is edible and harmless.
Re mushrooms:- I did notice that, after a while on the diet, that I found mushrooms less digestible than when on cooked diets. This was undoubtedly due to the antinutrients in mushrooms - some mushrooms have fewer antinutrients in them(don't know which ones). Perhaps soaking raw mushrooms for 24 hours, beforehand, as WAPFers do with seeds/nuts, would help re removing antinutrients.

Yes, I think most mushrooms come out partially digested, at least when raw. A lot of roughage. I watched a video about wild bears, and the mushrooms came out partially digested. They said bears ancestors are carnivores, not omnivores. So they are not fully suited for them as food. They were american brown bears. Yellow Stone grizzly I think.