In Leno's defense, smog checks for older cars can be absolute nonsense in CA.
I have an older car caught up in that nonsense. The header pipes cracked and replacement parts didn't exist so I had a shop build some. They did amazing work and function perfectly; it's just pipe about a foot long.
Anyway, the smog test shop sees that and fails visual inspection. That super sucks. There are no CARB exempt headers, and OEM is't available. I spent $$$ to put the old, leaking pipes back on, and send it back to the shop. Visual passes, smog passes. Next stop to the mechanic to swap headers back again.
At the moment there is a lot more to smog testing an older car than a tube up the tailpipe and actual emission data which is the whole point of having this program in the first place.
Leno likes cars, keeps his in great condition, and may simply need replacement parts manufactured that no longer exist.
Edit: that said, I hoped the Leno law would fail. I looked up registration for my older car as a "classic". Yikes that's pricy! And has all kinds of strings attached like special registration and have to be garaged. This would be devastating to the classic car community.