hello Roger,
at least I think, there is no real "miracle" behind that mixtures.
as far as one can determine, all those mixtures consist of fine grade composted fir bark, different grades of cocos fibre, (special treated) wood fibres, and little of natural compost and "fertilizer for 6 months", pH adjusted at 6.
I asked the Neudohum manufacturer, and they did not state there are any fungi added to that "composition".
The only "miracle" was the idea of "berthold" from Germany in terrorchid forum, to use that kind of organic soil for growing terrestrial orchids.
the Neudohum material is not sterilized, because sometimes "little black flies" come out of the material after planting....................
so, I think, you can mix your own "Neudohum/Silvamix", using that ingredients, which I mentioned above
But be cautious, it sometimes becomes "soggy"...............
(therefor I always add about 50 to 70 % Perlite or something like that)
cheers
cheers