[titzer]

It is a difference in kind: VW dynamically detected and adapted behavior to the test. It would never operate in that way under normal conditions. The water heater example was completely static: it always behaved the same way, under test or not.

[esrauch]

People obviously disagree since I was downvoted but I don't really see the black-and-white difference between the two.

In both cases there was an intentional design change to deliberately changed mislead a measurement, and the final product does not match the intended thing. Both adversarially directly cause the consumer's purchase to not be the intended item; no one gets a car that has emissions measured and no one gets a heater that has the efficiency measured.