I believe that is correct (although it might be more of a policy than a law). The manufacturers don't want to get sued because a driver that got injured/killed couldn't afford to repair a seatbelt mechanism.
Years ago, I had to buy a new belt for one of my cars because the buckle broke/fell apart. At the same time, I had the belts replaced for free on my 12 year old Honda Accord because they weren't retracting any more. Honda doesn't want to get sued...
varies from mfg to mfg... Jaguar warranties all of the motorized seat belts for life and anytime we see one coming in stuck forward its a race to be too busy to get that ticket.... other jags and as far as I know lotus too are only during the mfg warranty period, although i have heard of longer periods with japanese makers. a phone call to the local dealer will tell you real quick if they are or not..
if it retracts but slower, pull back whatever trim is covering it and see if it is twisted. many cars are designed in such a way that when they get twisted you wont actually see the twist and it will cause it to retract slower. ive seen the same complaint on several jags and found the thig twisted up several times.