I think this can be true of complexes under the current guidance too, though you are right, it could be clarified. I read the sentence you quoted as covering three example “and/or” situations:
- Species sometimes intergrade
- there are places on the tree of life where adding hard range map boundaries is arbitrary
- identification to species level is often not possible
Identifications of species Amanita bisporigera should only be used to suggest that single species. If you are wanting to use it to suggest “Amanita bisporigera or similar Amanita species,” then for now you should be identifying it as genus Amanita (with comment as needed), and proposing the creation of a new Amanita bisporigera complex taxon. Complexes are named after one of their component species, but they are not the same as the species taxon.