I would suggest that it depends on the 'personality' of the MNA, as well as structural risks and past adverse experience.

Some MNA just think they heed to control everything:  some dont.

Some MNA, for example those with 'federalist' jurisdiction like USA and Australia feel the need to at least provide guidance to their constituent associations.  Sometimes, certain constituent associations are identified as particular areas of weakness in numbers and qualifications of judges.

Some MNA have had past experience of denials of appeals miscarrying, for whatever reasons, and wish to prevent reoccurrence.

IMHO, there’s not much disagreement on what 70.3(b) is for: it’s there so a qualifier doesn’t get effectively “paused” by an appeal when a prompt decision is genuinely essential. The variation is about safeguards. I believe US Sailing treats “no appeal” as high-consequence and adds an approval gate; other MNAs are content to leave it to the OA/PC, as long as it’s clearly switched on in the NoR/SIs and applied narrowly.

So the format of a single event is relevant.  It's the purpose of the rule.

If there is a round robin phase followed by a finals phase, appeals are unworkable.  70.3(b) is required to ensure that the game doesn't stop because someone exercises their right to appeal!!

What about a case of a selection event, for say, regional / national representation 4 months later?  In such a case, 70.3(b) cannot be valid, since the condition of "essential to promptly determine the result" is not met. Conversely, a selection event for representation 3 weeks after may need this rule, so that flights / hotel bookings, entry registrations can be done.

That's easy to understand and pretty logical. Perhaps the RYA response.

Why then does there need to be 'safeguards'?  Safeguards against what?  Why should we stipulate minimum PC standards?

I wonder if some OAs try to use this rule to achieve the finality similar to 70.3(a) / 90.3(e) but without the expense of bringing in an international jury?  Perhaps that is what the safeguards are against... misuse of the rule by OAs to achieve closure/finality of results.

The Irish Sailing prescriptions state:
Denial of right of appeal under RRS 70.3(b) and (c) is subject to prior approval by Irish Sailing. Irish Sailing will not
consider the denial of the right of appeal under 70.3(b) and (c) unless the protest committee has a minimum of
three members, of which the majority shall be National or International Judges or Umpires as appropriate.

As part of the island is still (for the moment) governed by a foreign jurisdiction and its MNA  the requirement of 70.3(c) are rarely met!

Also from the Irish Sailing Prescriptions:
R2.5 ACCELERATED DECISION
Add new rule R2.5
If Irish Sailing determines that an accelerated decision is required for an appeal or request for confirmation or
correction, the time periods in rules R2.1, R2.3 and R4.4 may be reduced

Good responses.

I'm still trying to work out whether I go with RYA - - Why does it matter about the 'standard of the jury/PC'?  The concept being that 70.3(b) is a requirement for any event with multi-phases.  In which case, if an OA wants a round-robin followed by a finals phase, 70.3(b) needs to be activated.  Likewise, if one event is used as qualification to another, 70.3(b) is required.  No questions need to be asked.  (In fact, why isn't it just hard-wired into the format like Appendix D2.6(b)(2)(i).)

Or do I go with US Sailing  - - and believe that there is a tug of war between the "balance the need for certainty of results in an event with the desirability of retaining the right to appeal" and monitoring and protecting competitors from possible misuse/misrepresentation of the rule.
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In fact, I'm leaning towards a middle stance.

To me, 70.3(b) is simply a necessary technical rule modification to enable a certain competition format.  That's all.  I don't think the 'standard of jury/PC needs to come into the fray, since it is not really a question of denial of rights.  (The OA sets the standard of jury according to the competition it wants, just like any other event.) So I don't think it necessarily needs MNA approval in a perfect world.  However:

Consider this sample of some wording I have seen used in some SIs:

SI X - The right of appeal is denied per RRS 70.3(b).

I do think that, deliberately or not, sometimes 70.3(b) wording I've seen may mislead or intimidate competitors into thinking that they have no rights to appeal.  Perhaps, some OAs even kind of secretly like that wording for that reason.

So I think that the presentation of the rule in the NOR/SI must be kept clear to competitors what it means and the limitations of the denial.  Something like:

NOR/SI X - There is no right to appeal decisions that are essential to promptly determine the result of a race that will qualify a boat to compete in a later stage of the event, per RRS 70.3(b). The right to appeal any other decisions remains.

Such wording could be hard-wired into the prescriptions or sent as a condition with each approval.

(I notice that US Sailing does have suggested wording which also clarifies the remaining right to appeal when the conditions are not met.)

1.       RYA approval is not required to deny the right of appeal under rule 70.3(b).

2.      The RYA will not consider approving the denial of the right of appeal under rule 70.3(c) unless

(a)      the RYA decides there is good reason to approve. The cost of an international jury which would otherwise be appropriate for the event is not a good reason.

(b)       the protest committee is approved by the RYA.

(c)       application to the RYA is made no later than one month before the notice of race is to be issued.  In exceptional circumstances, the RYA may consider a later application.

3.      However, the denial of appeal shall not apply to a party to a hearing under rule 69.2, Misconduct, but the decision of the protest committee shall determine the results of the event.