Rear middle seat belt question

It’s a little thing, but I just can’t imagine why it’s designed this way. My '91 Saab 900 has three seat belts in the back. Two of the receivers sit next to eachother, and their position often gets reversed when I fold and unfold the back seat. They look identical, but the blade of the middle belt is slightly different than the side belt, so only with trial and error do I find which receiver goes with which belt. You would think that 50% of the time I would find the right combination on the first try, but somehow I never seem to! Why is there a bias? I’ve looked at the way the receivers are mounted to the car, and can see no reason why either belt should not be able to connect to either receiver. I know that this is designed in, and not some fluke, because I’ve noticed the issue on many other cars. Is there any plausible explanation for this -logical or not?

The engineers must have had a reason, but I don’t know what it is. The center rear seat belt in my Subaru station wagon is the same way. In order to eliminate the confusion I let the center belt and receiver stay under the seat cushion and only have the two outside receivers available. On the rare occasions when I have a rear seat passenger there is no confusion about which receiver to use. I’ve never needed to use all three rear seat belts, but it would only take a few seconds to retrieve the center belt if I needed it.

Does your seat belt warning system detect when back seat riders don’t have their seat belts fastened? If so, then it is necessary for each position to use the proper belt receiver so the system associates the latched belt with the detected occupant.

Obviously, Saab should have made the choice more obvious by making the belts and receivers more distinct from each other. Is there a surface where you could paint wrinkle-finish or similar paint so that the two center pieces would look and feel different without looking tacky?

No, there is no detector. Is this something commonly present on modern cars? I can’t imagine it was common practice in 1991, and I wouldn’t want it anyway, as I would always be dealing with alarms and warning lights when there was nothing but a beer cooler on the back seat. I could easily solve the problem by marking the middle catch up with a sharpie, I just need to remember to bring one down to the car. But I’m still curious as to why this situation exists in the first place. Makes no sense.

I’m just speculating, but maybe it’s vestiges of design features that did/do matter in some other use. Example: another Saab used/uses these belts in another model where the receiver position (i.e., side, or center) mattered/s; maybe that model had/s detector circuits. Then Saab uses the existing parts – already the correct length, attachments, etc. – in your model where the features do not matter.

With all this said, either leave the center belt attached to itself, hide the belt, or COLOR CODE the two ends that mate. Some colored plastic zip-ties might do ( my trick for tv cable i.d.), tape, or sewn on identifier.

I don’t need tips, thank you. I’m simply curious as to why the seatbelts are built this way!
Beam me up Scotty!

This is nothing new. In fact the Airline idustry has been doing that for years. The idea is so that you can’t use the wrong buckle or strap and thus not get the proper protection.