You have that story confused or backwards. Occasionally vehicle crash victims will suffer such internal injuries, mainly the elderly who already have weak blood vessels. But big cars don't have worse crumple zones, rather the opposite.
It's not "heavier vehicles", it's trucks. A lot of pickup trucks (and the SUVs based on them) were designed to prioritize load carrying capacity over occupant safety and have worse safety features than other passenger vehicles despite being heavier, and it turns out that matters.
