It’s not about the accuracy, since civilian surveyor GPS units are probably even more accurate than the standard-issue Military-grade systems. The key is the circuitry that allows the military version to continue working when the civilian ones get put into reduced-accuracy mode, and the components that let the mil system do things like ionospheric correction and encryption, and in particular the circuitry that makes military GPS receivers more resistant to jamming.
There is no longer a “military” mode or less accurate civilian mode. There is one mode. Can’t reduce accuracy or encrypt because the world uses GPS for everything and many uses are necessary for safety. Imagine going to an encryption/less accurate mode and those jets on short final on a Cat III approach. . .splat.
Therefore, there is no encryption mode for military users.
No encryption and anti-jamming on the units I used, from hand-carry to the units on my jet.