If you put any thought into this at all, you realize it is a massive conspiracy. Other automakers add expensive, space consuming devices to eliminate NO pollution. These is no way a single programmer could have made a change and all the engineers would go "Look, we don't need all the extra hardware, it passes the test!" Lots of people would notice immediately during the design phase.
Not really. A manager demands the feature in the software provided by Bosch, who warns him not to leave it in the final production, then they leave it on.
Not much of a conspiracy, but certainly a very deliberate decision from at least someone high enough to negotiate software deals with partners.