Yes you are correct-well spotted.
Of course, from the def on p 190 we see that SoR means that R is followed by S,
so if (x,y)ESoR then for some w we have that (x,w)ER and (w,y)ES.
Relate this to the example solution top p 173 in the guide, then we can think of S as V1 and R as (V2oV3)
So if we start the proof
(x,y)EV1o(V2oV3), then this means that (V2oV3) is followed by V1,
so for some wEX we have (x,w)E(V2oV3) and (w,y)EV1
etc.
We will give the full solution in tut letter 203.
In your letter you have the following:
v3 would map x to say w, so that (x, w) is an element of V3
v2 would map w to say z, so that (w, z) is an element of V2
The next line should be
v1 would map z to say y, so that (z, y) is an element of V1