There are definitely legitimate reasons for the Military to be conducting business CONUS. They are allowing exigent circumstances that units can do this for 72 hours before seeking approval. It's the fact that they are making a blanket policy that makes me raise an eyebrow. I'm not saying it is or isn't nefarious. I don't have any info to say either way. It is unusual. I worked in this sphere for decades and they were always very careful about violating posse comatatis. Probably not doing things that they could have done.
It just seems off. But that may be in part due to occurrences from the past few years.
I equate it to driving into my neighborhood and seeing someone who doesn't live there acting oddly and just being out of place. They aren't doing anything illegal but it's out of the norm and bears keeping an eye out on what else is happening.