OBDII has all the smog monitoring in the code, so the station only needs to hook the CARB tester to the OBDII port and let it run tests from there. No dyno or tailpipe sniffing required. I have several OBDII cars and they have never had the sniffer inserted. And the test price is cheaper than OBDI.
My Z32 is a '90 so I look forward to this law, it will save me the "prep" time before taking it in.