Seeing that no one took that bait, I'm completely spitballing here:

It seems that the technique used by this pest abatement contractor is the "apply pesticide everywhere and hope that you'll be sure to kill everything that might enter the structure from the soil" technique. I admit to having a question if that is strictly really necessary. Rather, it seems to me that a properly installed crawl-space radon depressurization barrier should:
1) if intact, be proof against pest entry across that barrier and through the barrier-foundation seal.
2) but if such a barrier is compromised by pest entry, it seems to me it should show evidence of such breaches relatively clearly, which can then be addressed.

My recommendations would be:
1) Find out if this pest-abatement contractor's approach is uniform across that industry or if not, find out how other pest-abatement contractors handle the issue. Perhaps they have a more surgical approach of applying pesticides at the points of infestation rather than to the entire structure.
2) Find out if any pest-abatement contractor with an open mind about possibly changing their abatement technique would be willing to work with a similarly solution-oriented radon mitigator and do some pre-/post- experimental work in a few buildings, if the homeowners would be willing to cooperate.