Nahh. Tailpipe emissions testing just looks at what is coming out of the tailpipe at the test station under minimal load. There’s no way to simulate the actual driving pattern of each customer or what is happening when the car is driving at 60mph.
A tailpipe test won’t show that your car was running at 2.5% CO for 25 minutes before you got there because your thermostat is stuck open and the engine is cold. A tailpipe test won’t show elevated HC caused by an intermittent arcing plug wire because there’s almost no load on the engine at the test station. A tailpipe test won’t show a sticking EGR valve if it happens to be working at the test station. OBD2 shows a history of events and long term memory of what’s going on.
Tailpipe testing does nothing to address evaporative emissions.