I agree with the comments answering Andrew's question. There are a couple of further points I would like to make - I'm the person responsible for judges training in New Zealand.
One mistake I see a lot of sailing officials make, when considering how the rules apply to factual situations, is to go to the casebooks before they properly read the rules themselves. Remember that the cases and calls are applications of the rules to particular facts. If you don't clearly understand what the rules say in the first place, you will not understand how they will apply to the particular facts you are considering. You will also not understand how the cases and calls are relevant.
To clearly understand what the rules say, you cannot read them like you would read a newspaper or internet article. You need to break them down into ingredients or components, understand what each component means, and then see how each applies to the factual situation. To understand each component, you need to consider the qualitative terms such as "room", "keeping clear" and "proper course". If you do all that, then in 95% situations, the rules will themselves answer your questions, and cases can be used to check whether your interpretation is correct. With respect, if Andrew had done that, then that would have answered the problem in his scenario, and he wouldn't need to look at MR Call G2.
Jacob, when you say MR call G2 is "valid" in Andrew's scenario, because it refers to a rule not changed by App C, are you saying that such Match Racing Calls are authoritative and binding in fleet races? If that is what you are saying, then I disagree. The reasoning behind Call G2, and similar calls, may well be relevant to fleet racing scenarios, but they do not need to be followed as an authority.
The Introduction to the RRS expressly states that the Match Racing Call Book is only authoritative for match racing. This is also the case in the 2021-2024 Rules.
The introduction to the MR Call Book itself acknowledges that there are differences between the disciplines - "In drafting the calls, care has been exercised to minimise the difference between Fleet Racing and Match Racing in terms of the Right of Way Rules of Part 2, however it is recognized that Match Racing is a separate discipline and that there are some differences from Fleet Racing. It is important to note that this Call Book, like previous editions, is therefore only authoritative for umpired Match Racing".
Again, the call books and case books concern the application of the Rules. The way in which rules apply to a match race may differ from a lot of fleet racing scenarios. Also, a lot of the match racing calls are concerned with making the rules usable for umpiring.