You may be correct regarding the police testing.
I am going by Skan's website that states:
"SKAN CHRONOS HAVE BEEN IN CONTINUOUS USE WITH UK POLICE FORCE AND AIRGUN MANUFACTURERS FOR THE LAST 26 YEARS"
Whether the police themselves test using them or refer the guns to independent laboratories that use them, the end result is the same. If it passes with your own Skan you may be pretty confident that it will pass with any other Skan being operated by the Police or their chosen representatives.
I feel that you are in danger of "throwing out the baby with the bathwater" in suggesting that it is pointless testing with anything other than a very expensive and complicated radar setup.
As most of us build in a margin of around 0.5 to 1.00 ft-lb of muzzle energy, we are probably safe from most minor variations between chronographs.