Agreed, but it's not about the brand - it's just that in the market segment for a $35-40k mid-size sedan, there's not a whole lot of need to wait two years for a car, which is why it's so uncommon. The reason it doesn't happen to other manufacturers, is because although they have 3-4 year lead times on new models they produce, they're still continuously producing the current models
Don't forget about two car households. We have an x1 and an i3 as our commuter car. The i3 will eventually be replaced with a Tesla, the x1 will not.