A few points are worth mentioning when considering this article. First, and foremost, are considerations for the buying behaviours between durable and non-durable goods. Cars do not tend to be an impulse buy, and I'd argue that a large proportion of buyers have multiple selection criteria - beyond just "new" design or technology. Whereas non-durable goods are much more susceptible to impulse buying which, in my estimate, are better influenced by design and technical newness. Thus, I'm arguing that the article is only sub-market focused/useful.
Next the authors use Europe, where the CO2 emission value has an enormously significant affect on buyers' choices. This wasn't a control variable! But this also highlights the fact that buying decisions can be notably different between regions (MPG tends to be further down the criteria list for most ICE buyers in North America). How were both scenarios (high priority buying criteria, and regional differences) considered, and compensated for, in the study(?). This bridges to your sustainability question.
Third/forth - it seems to me that they should have removed "bad" new designs or technologies from their data. There are plenty of examples where a new design or technology was poorly researched, and subsequently received, in the market. These were faults in execution by automotive companies, and it would have been simple to control for (automotive reviews are quick to damn 'bad' introductions).
Finally, pricing (cost delta influence) of the new technology or design features (not just the 'base' vehicle costs that were used as a control variable in the study). The majority of the time new technology is an option for a car, and some of those options have a hefty price tag for them. Same goes for design enhancements (rear wings, special colours or materials, trim additions, etc.). How are these very common scenarios reflected in the study? If anything, this would be the easiest data (base vs. new tech/design options) to prove their thesis. No doubt the automotive industry understands this intimately.
Nevertheless the finding - that innovation generates higher sales - is sound (in the aggregate), and reinforced by the abundance of studies that have done a good job of proving the relation.