So one could just throw plants into water and let it sit?
yea bascially, but specific plants have benefits over other plants, for example nettle FPE will give you much more benefits than say grass FPE.
All of the additional research on FPE I've done is saying that adding EM to the mix is a MUST
no, thats silly. ive used extracts without EM for years.
I guess it kind of makes sense, because I don't really know where the bacteria to ferment the plant material would could from otherwise.
bacteria and fungal spores are on just about everything on this planet, including plants and even inside plant leafs.