I always thought the old rule was kind of strange.  You had to inform them either before or after finishing.  I guess you couldn't inform them at the instant they were finishing and have that count.  As the first reasonable opportunity is not linked to finishing then you don't need to include any of that in the rule.  There is no functional change to the rule, it's just simpler now.  The only question becomes when was the first reasonable opportunity.

I'm not sure Answer 3 of Case 112, quoted above, is clear on the issue of when a boat has to inform another boat that she will protest under rule 28.1 Sail the Course, because it still leaves open the question of when is the 'earliest opportunity'..  The statement from Case 112 that I think clears up the issue is the italics at the top: 'A boat that makes, and does not correct, an error in sailing the course does not break rule 28.1 until she finishes. If a boat makes such an error, a second boat may notify the first that she intends to protest before the first boat finishes, or at the first reasonable opportunity after the first boat finishes.'  According to my reading, that means that the protestor may notify the other boat at any time before she finishes of her intent to protest, or may wait until the earliest opportunity after that boat finishes, to notify her, and in either case the protest committee must consider the notification to satisfy rule 60.2.

John C,  The background to Case 112 was that some time around 2008 there was a Q&A, initiated from, I think, the USA, where the answer was that the requirement was to inform the protestee at the first reasonable opportunity after making the rule 28 error, that is, missing the mark etc.

It was then discovered that the RYA had a long standing Appeal in their Appeal Book that more correctly identified the time of breaking the rule as when the boat finished, so that time for informing the protestee needed to run from not before than that time.

Case 112 was then issued to unwind the Q&A and clarify that the RYA interpretation was correct.

The wording inserted into the RRS in 2013 appeared to make Case 112 redundant, until the 2025 RRS deleted the qualification ‘after the [protestee] finishes’. 

Suddenly Case 112 became important again, because, as Rob O has said, it explains the rationale and makes the 'after finishing' qualification clear.