I was trying to meta research the use of pine shavings for animal bedding and for growing mushrooms. There seems to be too much hearsay online and no concrete evidence for the most part of anything. Then I came across this article that deeply details the entire thing about using pine shaving as animal bedding. So, I'm passing it along,
https://mushroomrattery.weebly.com/wood-shavings.htmlThe tl;dr version is that pine shavings don't cause problems with animals simply because they are pine shavings. Problems the animals have are secondary, like not changing the bedding as often as you should be doing; which is typical with any bedding type. And so, using pine shavings is fine for animal bedding.
I'm still trying to find info on why you shouldn't try to grow mushrooms in pine shavings. Common sense tells me it is because only a few types of fungi actually eat pine while others are unable and simply don't do anything in it.