I don't think you are correct in stating that the touring RGS didn't have a QD headlight.
If you look at the road test from 1962 the plug can be seen and the bike is a tourer.
Trev, well spotted! You are quite right. A close study of the 1962 road test photograph does indeed reveal a QD headlamp as being fitted, and the featured bike is definately a tourer because it is not fitted with rear sets. I had never looked closely at that photograph before. Well done mate. I made that statement on the basis of information published in a magazine article on how to spot a fake RGS (written by by a supposedly noted RGS expert). Interestingly there is no mention of the headlamp or wiring harness in the RGS parts list of April 1962.
On the more general topic of parts and fittings, in the Gold Star parts list that I have for example, there is no mention of a QD headlamp. Two headlamps are listed with the part numbers 19-543 (R/H dip) and 19-529 (vertical dip) and the illustration shows the U39 switch as being fitted. In the real world I have seen Gold Stars in Clubmans trim fitted with QD headlamps and with non QD headlamps, and Gold Star tourers also equiped with both QD and non QD headlamps. None of them that I have seen have ever had the U39 lighting switch fitted they have always been fitted with the 41-SA type. The reasons for this are probally because people have fitted whatever was available or what was affordable. Who knows? For reasons unknown BSA choose to use the the same illustration even though it might not depict the actual part described in the part list. Misleading information can arise due to many reasons, and that is one of them. All anyone can do is to research as thouroghly as they can. Even then it is possible to get it wrong.
Taff, I agree that many of the weaknesses in the QD design in this day and age are not that important, and although a few were raced all those years ago most were not. The QD headlamp facility was more likely to have been added as a "go faster" option rather than any serious attempt to make the bike a out and out sportser. Of one thing we can all be sure. No matter how hard we try to get our bikes right, there will always be somebody that wants to find fault.
John