Pretty true. As I recall, the Federal requirement was to provide either airbags or motorized seatbelts (remember those contraptions?). A shoulder-belt plus airbag is certainly best, but a shoulder-belt alone provides most of the protection.
Those mainly help when the driver runs into something and help little if struck on the side, which is my concern since I never run into things. I would rather be in most 60's cars in a side impact than a smaller modern car, unless it had side air bags and a protection beam. A 4 door or post model is much better. I saw a 69 Dart 2 Dr hardtop just like mine that was hit in the side and the door folder in on the driver.