Terrifying seems a really strong word for the difference in severity from FF to RF in a car. You're still protected by all the other safety features of the car like the crumple zone, anti lock brakes, the solid frame, anti collision systems etc etc.
Genuine question, do you find people cycling on the road with a baby/toddler on their bike "terrifying"?
Because that'd be a much more severe crash, in the unlikely event of a crash, than a forward facing 5 point harness seat inside a car. There are none of the safety features of a car, but you're on the road with other cars.
Where I live, South london, lots and lots of people do the school run with their kids on a bike, including small toddlers.
And yet none of them seem to attract the same safety-related-disapproval of FF car seats.
I'm not having a go, I just find it really interesting.