"Most likely to be" != "Totally this"
Just to be sure we are on the same page here. I am not ruling out fungus as an option, just saying it is less likely to be the case. (what is the fungus eating in there? I needs a source of metabolic energy. Unless this is some very strange chemotrophic fungus or something, how do you explain having a fungal growth of that density, in the absence of organic substrate? Etc.)
Zapping it for science is the most direct way to find out. Sadly we may never know.
vis-a-vis "Lamplight"
It is also a theatrical term for purposefully drawing attention to something in a narrative. This is the use I invoked.
An example in television, is a close pan-in to a McGuffin in the scene, even when the actor's characters are unaware of it.
You might be thinking of "to
highlight", but I can't find any examples of someone using "lamplight" as a verb.
In any event, I'm not saying your conclusions are necessarily wrong. I'm saying that you and the author have collectively managed to demonstrate why you don't bring up Occam's Razor in a scientific context to discriminate between candidate hypotheses: because ultimately it's a judgement call working sideways to the actual process. "Most likely to be" is indeed not "definitely this", but it's also not scientifically meaningful outside of very specific statistical contexts.
I'm not doing this to pick on you, by the way. I'm doing it because adversarial reasoning like this is probably the single most pervasive and tenacious error people make in trying to think scientifically, and it's a weirdly subtle error for something so core to empiricism; the same processes that are vital to organizing and prioritizing research are fatal to actually performing it. You've helped to provide an unusually tutelary example of why that is, and I felt it was important, in light of how we're all looking at the pseudoscience now, to highlight that.