That makes sense. In North America, '68 was the first year the venerable 123GT (and likely also the 122S maybe even the 122, I forget) got clamp-over front head rests (not yet integral to the seat frame), so likely the first year that rear seatbelts also became standard, although there could have previously been attachment points for rear belts in other markets. My research suggests that Volvo was the first manufacturer to introduce rear seatbelts in the 1967 Amazon (122) in the Nordic markets.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now