Paging the expert.
The so called “discovery” is many years old, rehashed again. Despite the mushrooms in the picture, they have no way of knowing what they looked like. Mycelium is indeed different from other cells in size and complexity, something that was not covered. Where are the spores? All fungi reproduce through spores with spores from different groups having distinct characteristics. Basidiospores have an attachment peg, a cleft where they were attached to the basidium. Ascospores have no such feature. Asci have a detachable operculum, the opening where the ascospores emerge. But an operculum is also found in Oomycetes, on a sporangium or sporangiospore, where the zoospores emerge; zoospores also have flagella. These structures could have been anything, calling it a giant “mushroom’ is pure conjecture. The largest mushroom known today is only two feet in size (Macrocybe titans, https://sites.google.com/a/simplescience.info/www/biology/fungi). So where did these giant “mushrooms” go? Simple conjecture, nothing more.
May the void once again prove its nullness.