Im not sure I agree with you on that one (well not completely).
I do remember time and time again we got this hammered into us at school - "Answer the actual question that is asked and not something else" and I remember that well.
Its no good writing reams and reams of calulations to show the answer, in fact you could actually arrive at the wrong answer but show youve actually followed the correct procedure and get a higher score for your endevours than just getting the answer correct but following incorrect procedures.
With that in mind I would tend to take your stance.
(with this in mind, on a test, we had the question "Do you know XXX ?" I did not know that so I answered "No" and there was no amusement or debate about my stance that I had actually answered the question asked correctly .
Our teachers took no prisoners back then and the outcome was very stern to say the least!)
The way I see it (I think you might disagree) is :- answer that correctly answers what is asked about the ring/radial shown and the inclusion of 3 sockets should be considered as a correct answer, there might be only one answer to a question yet there might be more than one correct answer too.
So long as a correct answer is given to what is asked even if it does things not actually asked for make that answer actually become incorrect?.
I would not expect additional marks for irrelevant additions but does that render any correct part of my answer to be actually wrong rather than merely not required?
I strongly suspect that you might well have been educated to a far higher level than myself but I still think I might be correct.
My observations on that one (1/, 2/, 3/) -
A Ring might be awarded that name to either a Ring Final Circuit or a Ring Main.
A Ring Final Circuit we all know and love (or hate!)
A Ring Main might mean wiring in the streets supplying the mains side to a number of houses in the estate and the Ring part of it is to combat volt drop as its prime consideration, whether or not there is an intention to allow isolation of a section of that ring to allow for repair/modification to an isolated section safely whilst having a minimum disturbance to the remainder we dont know.
A Ring Main on the Transmittion/Generation side of things might actually refer to a number of supplies incomming from various sources, the cables sized as for a Radial but isolators each side of every Generator in order to allow one Genorator or a number of adjacent Genorators to be locked off out of circuit for such additions/modifications/repair etc.
Yes as per your "more likely way to to increase the capacity of existing 15A radials with a quick and easy mod?" then yes I agree but that does not exclude that other alternative reasons might apply both jointly or severally.
