IMHO rudder was re-skinned, ribs were taped and it was left unpainted.
Could be, but to replace an intact skinning is much more expensive than repainting it.
Yes, but it is a critial control surface.
An example, in the 1930's the RAF had problem with their Hawker Fury's, which had painted control surfaces, and as they were kept immaculate in time the paint being continually touched up, which led to problems, maybe even crashes..[this is from memory, must check from where later ] leading to the RAF bringing in regulations saying not to paint on control surfuces, except whe a complete repaint was done, and I presue contorl surfaces could be checked for their balance. And with very few exceptions, this was adhered to since then. [only one coming to mind, Hurricanes in France in late 1939 with French style rudder stripes]
I digress, my point is a badly painted over rudder could cause control problems, and I don't think you can easily strip dope off fabric, so a recovered or replaced rudder is only option.
Or simply a recovering because of damage....
Never seen this about Sopwith Snipes before...very interesting.