Yes that initial start is richer.It also supposedly cuts greenhouse gasses; obviously when the engine is stopped, but when restarted, aren't the initial first revs use a richer fuel mixture until the engine is up to idle speed?
The gain is very little unless cars are sitting in traffic for long periods. I can see the benefits if all cars sitting in traffic do start/stop.
I'm in that camp where if people REALLY want to cut down on greehouse gasses or "carbon footprint", or if the politically correct elites of America really wants to cut down on emissions, then why are all these companies forcing office people to drive back to the office? When we had COVID lockdown, the air was so crisp and clear! All those vehicles were off the road. Only essential vehicles were usually out on weekdays. Now that would REALLY make a difference. But now we're all back to driving to the office daily, sitting in traffic, wasting fuel and emitting exhaust. WTF.....we learned nothing.