I was initially told by the Southwark Highways team that it was a legal requirement, and they had no choice. However, they later reduced the yellow lines on my section from 10m to 7m, indicating that it was no longer a legal requirement.
I did file a complaint and also requested an extended yellow line at one of the junctions with Lordship Lane, as it was difficult to see when turning right. I received no response, and it took five years for that request to be addressed.
I agree with your point about my generalisation of Southwark Council – I should have been more specific, particularly when referring to the Southwark Highways department.