It was intended to be a very generalized statement, which as you said in a perfect world, you wouldn't have to grow the microherd in theory. And remember in theory, theory & practice are the same, but not in practice.
If you recall I alluded in the beginning of this thread to the overall emphasis of the subject matter is based on a statement of a noted and very well respected microbiologist, regardless of OUR, your and my experience and others experience collectively of operating on a different mindset.
So is Elaine just theorizing or is she correct when she says all your plants requirements to grow, every nutrient they require from A-Z is already locked up (insoluble) in the clay, the silt & sand? This is a rhetorical question in case there is a question about the question, no question!. Of course if you are hydro farming with coco in a flood in drain this is not applicable to you, but if you are building containers one may want to rethink their approach which most take of mix and bake and soil ready to pop in plants, sure it works but if you have grow tired of doing the same work and perhaps, you are like me work smart not hard, there has got to be a way to incorporate what you astutely noted happens outdoors with natural composting the return of food to the soil, beyond the exudates from the roots for winter feeding if you don't mind the term.
So this bring up a very notable subject for me SIP, self irrigating planters. I've incorporated them indoors on a larger scale then a typical planter, with the idea of reproducing this carbon cycle you and I are well versed in.
DANKSWAG