I think there is just too many factors/variables the ‘2nd vehicle’ that it makes the study perhaps not useless, but severely diluted at best.
I will use myself as an anecdote. We have 2 cars, one being a ICE fleet company vehicle. My next company vehicle will be ICE unless there are affordable (read: cheap and available) EV with double the current available range. Because of this I would fall into the ‘go back to ICE’ category. Yes, this is a somewhat unique situation, but there are tons of other unique situations that this would apply. Not to mention half ton trucks where electric options are limited at best.