[1] The naming history of this mushroom is complicated by the fact that for a long time it was regarded as two different species, "flaccida" (associated with broad-leaved trees) and "inversa" (associated with conifers and with a smoother shinier cap).

[6][7] The new genus is recognized by Species Fungorum,[5] and the Global Biodiversity Information Facility,[8] but not necessarily in derivative databases such as the Encyclopedia of Life.

Older mushroom references generally listed the flaccida and inversa forms as separate species,[9] but modern authorities merge them into one.

[8] The inversa form is sometimes regarded as a separate species, in which case it is distinguished because it grows under conifers rather than broad-leaved trees, has a shinier cap surface, and is more rigid (less flaccid).

[11] P. flaccida is also similar to the edible Infundibulicybe gibba which has thinner flesh, less crowded gills, and (microscopically) smooth teardrop-shaped spores.

P. amoenolens has a strong characteristic smell, a beige colour, and a less depressed cap; also the spores are smooth.

[17] An article in Nature Communications reports that an extract of this mushroom, with active constituent 2,6-diaminopurine, can correct RNA nonsense mutations and so may be a candidate to help treatment of certain genetic diseases.