Isn't the issue that some people work around MOT decibel limits? After all they only need to pass the decibel limit on the MOT test, and not on the road in regu

Isn't the issue that some people work around MOT decibel limits? After all they only need to pass the decibel limit on the MOT test, and not on the road in regular use. The engineering solution approach doesn't seem to be fundamentally different to speed cameras.