The softer woods and stem materials, certainly the sawdust's, paper, and grains are "fast food" to these species of fungi....they tear through them and consume them very rapidly......
Which acts, as Hyphae has said in the past, as super highways for them to run throughout a bed/substrate.....the softer and more porous materials (including various soils) also act as moisture reservoirs......
As with most other substrates that I've worked with and used, keeping most of the bed "fluffy" and loosely built seems to give these guys exactly what they want....
The oak and other hardwoods are very dense, thus the meat and bones of the meal......it's plainly visible in the pic that this fungus has absolutely decided it will consume the oak.....which is very dense and heavy..
Each block weighs over a pound and they have been baked at 340 F for at least 14 hours...it's more like two lbs each BEFORE the fertilizer water soaking...
This is clearly a type of hugelkultur.....the bottom of the "hole" is lined with cardboard....a layered bed of spawn and substrates (soft and hard) is built....in this case about 14 soaked oak blocks were added right at the "surface" but additional layers of soil, grasses, old mulch, dead/wind fall branches, debris, and etc are acting as cover....think like an overhanging creek bank...what happens there???
Layers of organic materials are added to the "top" and the entire thing is kept very well watered....drying of beds or any substrate for that matter is seriously detrimental to their health.....
In fact it's attacking everything woody within it's reach.......they almost always do and surely they run away too....not to mention the spore load that gets blown to the farthest reaches...
And it seems they will generally explore to the extents they find possible.....All they need is to have the advantage over the other organisms to start with (which is what the hired help (US HUMANS) do)......
How far will they run???..... I bet FAR and wide....
A