It's not the individuals doing the study who are cooking the books, it's the NPS who is counting passive resistance and failure to comply as assaults against LE. The social scientists on the NPS payroll just lack the balls to tell LE that they are a bunch of pussies.
But this way the DOI can complain about the ongoing plaque of assaults against their LEO's, and get M-16's so they can enforce order in the Forbidden gully.
According to the report, Yellowstone had the highest number of LE assaults. Having spent several July's in Yosemite in the 80's, you could get a beat down by the bikers there. It's hard to imagine that Yellowstone is such a difficult place for LE, unless you count hurt feelings as a serious attack