I agree with the last paragraph and would add that they also don’t want people putting anything but very light objects on the roof. That means they can cut corners on roof strength, as long as it is just enough to prevent squashing occupants in a rollover.
My fuel conservation consists of reducing total miles driven, combining errand runs, and driving smoothly, no speeding.
If you visit this thread: Roof Tent? - Advice - Paddling.com there is a discussion about roof strength, static load and dynamic loads. There are also links to several sites that discuss roof strength tests, etc.
I do not wish to reiterate all of that so, I will just say that newer vehicles must conform to a higher strength test than older vehicles did. So roof strength to prevent squashing occupants (as you put it) is increasing not decreasing.
We love our Subaru Ascent!
Subaru says it is an SUV but that’s just marketing. I’m not sure what it is. It is huge, much bigger than an Outback. It does have a spoiler on the lift gate but I set the memory to not touch my Cetus and I can stand under the lift gate in that position. (I’m 5’ 11")
It is also a great road trip car, exceptionally comfortable.