This is a myth. There have been massive improvements in safety design and some tiny cars do surprisingly well in some tests against old cars of any size - but modern SUVs are much safer than a modern tiny car, and improvements to the strength of the safety cage in large vehicles have offset the improvements in smaller vehicles. Relative vehicle weight is still the biggest predictor of occupant injury, and the types of impacts that kill occupants (small overlap and side impacts) favour higher ride heights. There is no trick engineering that can protect the occupant of a tiny car from a 2 ton SUV going through the side window. You can see this in the data for average death rates (https://www.iihs.org/ratings/driver-death-rates-by-make-and-...) - the death rate per million registered vehicle years for mini cars is more than double the rate of SUVs.

Some work has been done to study this, you can find some links to papers here: https://en.wikipedia.org/wiki/Crash_incompatibility https://skeptics.stackexchange.com/questions/6698/are-big-ca...