Isn't "uniquely describing" something just a step in the process of identifying something? I.e., once it is uniquely described, it can be identified. In reverse, identification can be directly achieved by quoting a sail/hull number or by determining the sail/hull number of the only pink boat in the fleet. I see this as synonymous in the context of 60.3(a). However, the problem with this is that it puts the onus on the PC to convert a unique description into an identification, which is in my opinion is undesirable.

Generally agree with John Allen on all of this.

I have mountains of educational material which needs updating, but on the whole I think the rewrite is more fluid. 

B

Isn't it as simple as - both boats enter on port tack into the zone - so their is no other boat on starboard tack.... as 18.3 requires. So it boils down to rule 18.2 not being intor effect for neither of them. Rules 10, 11, 12, 13 and 15 will apply for what continues. There is no Zone, there is no 18.2 - both are tacking in the zone and turning 18.2 off. 
From the picture it appears as Yellow made a clean tack to starboard, Blue has to give RoW. Blue is entitled to luff Yellow when overlapped. But Blue cannot tack.

That is how I see it now if the mark is to be left to Port

Robin re: "I would argue that a boat that is in the process of tacking onto stbd so as to pass a mark is not "in a position" to pass the mark as she is not able to set a course for it until she is close hauled."

Yep .. that's definitely where we disagree.  Let me give you my best shot on it how I see it.  I'm repasting your 1st drawing for our convenience.

My first general response is that there is nothing in the def: fetching that requires a certain a point of sail in its determination.. and beyond that nothing as specific as a "close-hauled" requirement.

Further, let's look at position #4.. Here are my Q/A/C.

Question: From position #4, after they each pass HTW, can both Yellow and Blue pass to windward of the mark and leave it on the required side without changing tack?
Answer: Yes, at position #4, both Yellow and Blue are clearly on or above the starboard lay-line, which generally indicates the path a boat can sail toward the mark on a close-hauled course to pass to windward of the mark.
Conclusion: Therefore, at position #4, both Blue and Yellow are "in a position to" do so and thus are both fetching the mark..

If we interpret "cause" to essentially mean "compel", as Greg and others do in this thread, we negate the change to rule 14 for 2025.  When a boat runs into another boat or into an object she should avoid, that is rarely if ever "caused" by some other boat, in the sense of "uniquely caused".  In the given scenario, one cause of Red's encounter with the RC vessel was that she went in there in the first place,and another is that she chose to hit the RC vessel instead of fouling Blue.  If we take that tack, then ironically Blue is only subject to rule 14 if Red hits her, which is the pre-2025 interpretation.

On a tangent issue, Cata, how did you make that incredibly great diagram?  If there's an app that does that, we all want it!