This use of the gate on the second downwind is because there is often more than one fleet using the outer leg. Eg One going to finish and one turning to go back upwind. The RC does not want boats approaching 3s from opposite directions. 

I will attemp a guide next week, at an event at the moment. 

Ben,

1. I enclose an extract of relevant portion of Case 50.

A starboard-tack boat in such circumstances need not hold her course so as to

she does so she will break rule 14.

The fact that L took action to avoid collision at a time when W also initiated action implies there was an apprehension in the mind of L. W, as per me, took the action late.

2.  Case 50 does not say anywhere that it can be applied to rule 11.

Thanks for your thoughts, @Christopher Walmsley.  To the question you pose regarding the situation where Yellow is 'moving slowly, or almost stationary' then I would suggest Blue has the option to 'pass' on either side but then has to satisfy 19.2 (a) and 19.2 (b).  Presumably if Blue chose to bear off and 'pass' a slow moving (or stationary) Yellow on their port side, remaining on port gybe, she is obligated to leave room for Green to do the same, 'unless she has been unable to do so from the time the overlap began.'   In our scenario, however, I would contend that they were unable to 'pass' Yellow by bearing off and only had one side they could have chosen. to 'pass'.  I do think they exercised a third option .... to 'avoid' by gybing which, as ROW boat they were free to do.  If they chose instead to 'pass' Yellow on their starboard side (the only side they could 'pass' the obstruction in this case) by heading up, then Green is burdened potentially both by RRS 11 but also by 19.2 (b).

That leads to one further question in my mind.  We don't know how the overlap between Blue and Green came about, however if Blue came from behind to establish the overlap (before the diagram starts), are they relieved of their obligation under RRS 17 with regard to Green by RRS 19.2 (b)?   She certainly sails above her proper course to take Yellow's stern if she heads up to do so.   

"If the details included remove any ambiguity about which incident the delivered protest is referring to"
Clear as mud.
Does not answer the question.