I expect this to be the start of a trend based on my own personal experience. I bought some "compostable" bags for my kitchen scrap bin that I would then dump in my outdoor composter. Six months later when I went to get my compost, large pieces of bag not only remained but had harded into solid chunks. Took an hour to sift out the chunks from the compost.
Edit: turns out I was ignorant of how they actually work.