I'm not sure the claim is true. I only have one personal experience to base this on (fortunately) but I was in an accident as a passenger in a Jeep Wrangler which ended up upside-down on its roll-cage. Both the driver and I were hanging from our belts and had no problem undoing the buckles. We had to do it one-handed with our other hand trying to support ourselves so as not to drop on our heads after releasing the buckle. Click, release, just like normal.