I think the issue is that they really can't test for real world emissions, so they use a combo of idle/low load limits, along with specific equipment requirements. It's a sweeping broad brush that accomplishes its objectives in the aggregate, but with lots of illogical/non-sensical individual results along the way...much like many regulatory systems....

 

Just got an invoice for my cats, so I can show it to the inspector and hopefully not have any issues.