What we both see is (1) a drawing of a totally fictional process of gluing silica to spores with "polymerized glass" and (2) a spore covered with bits of crushed fumed silica.
If van der Waals forces were a concern here, those forces would be defeated by the total irregularity of the coated spore. There's simply not enough flat surface area where one such coated spore can significantly touch another such coated spore (the same effect that the evenly spaced bits would accomplish).
The Duway example seems to be irregular bits of crushed fumed silica piled upon other crushed bits. There appears to be silica attached to silica. And the silica bits appear to be fused together. That's VERY different from the evenly spaced, glued-on silica particles in the fantasy drawing.
The Dugway example results from MIXING fumed silica with spores and then pounding them and running them through filters. The silica bits aren't glued on. They could be either stuck to the spore as a result of static electricity or some effect of pounding the silica into the outer coating of the spore.
The co-author who wrote me yesterday suggested that "physical bridging caused by water in the air" [i.e., capillary action] could have had some effect on interparticle bonding. But, he said there was disagreement among the co-authors as to what holds the particles together.
If the "experts" at Dugway can't agree on what is doing the bonding, I don't think we should just ASSUME it's something that fits some belief.
The silica could be fixed to the spores by the pounding action of the ball mill. The bits of silica could be pounded into the latice-like outer coating on the exosporium. Think of it being like sticking a tennis ball into a chain-link fence.
I'm not saying that's the explanation, but it certainly seems to fit VERY well. Water would soften and expand the exosporium, releasing the silica.