This is one of my favorite ecological interactions. There is a lot of speculation about what exactly is happening, though the relationship involves two mushrooms, an Amallaria, usually Amallaria Mellia(The honey mushroom) and any number of entaloma species. One of the two parasitizes the other and professional mycologists love to argue and speculate about which parasitizes the other. From my experience the partially aborted forms have all the trappings of the entaloma genus having pinkish gills and a boring grey hue, so it is my opinion that the honey mushroom is the one doing the parasitizing, which I think stands up based on the fact that they are prolific, fast growing and generally parasitize trees, so it aligns with their ecological habits. Anyway, whatever is happening is very interesting and maybe because we don’t really know what is happening.