If they are anything like the American Meat Institute, you're probably right.

Just cook them well.

I've been blessed enough to grow shiitake in homemade sawdust blocks, and my goodness, they are fantastic! I've tried several times to grow portobellos, and they never grow for me. But I will probably keep trying. Because they are indeed fantastic and make a great meat substitute.

My family calls them hippy dinners....No meat. lol.