Not all rule changes are made equal, Some rule changes have a much more wide-ranging effects than others. The first turn rule change is a much bigger deal than the bench damage ruling.
Example:
- The 19th amendment allows women to vote. <- A big deal
- The 27th amendment prevents congressional salary changes from happening until the beginning of a congressional session. <- Not such a big deal
They're both amendments, but one is a much bigger deal than the other. Just because they're both changes to the fundamental rules of the game, it doesn't mean that both are equally important.
While your example is well taken, the Constitution is there to protect the rights and private property of those under its jurisdiction; that is to say, every time the Constitution is amended, there is a clear purpose; to make it better at protecting those things.
When the rules of the game are modified, there is a slew of reasons for which it may happen. Sometimes it's to make it fairer. Sometimes it's to make it simpler. Sometimes it's to market a new specialty card (Pokémon Lv.X, for example, were given an exception in the Meta-Ruling about copying attacks). These ends contradict each other often. I don't think there are many who think the recent rules change was unambiguously good for the competitive scene, or even designed to improve it (the primary motive seems to have been simplicity). As such, the degree to which a rules change affects the competitive scene cannot in all fairness be used to determine how much of "a big deal" a rules change is.
While keeping the game in balance may be a secondary effect of Meta-Rulings, the primary purpose is, without a doubt, to help players play the cards correctly. Having a misconception about a card effect is bad enough in a tournament with judges, but potentially game-ending to casual players who don't know how to resolve a certain card interaction. Thus, the Compendium. Because of this, the primary concern we should have in mind is not whether the ruling significantly affects the format, but whether there is potential for ambiguity in a casual game. Even here, I'll grant the first-turn rule is likelier to come up in a casual game, but the Hone Claws ruling holds plenty of potential for ambiguity and it is thus very important that the Compendium be correct with regards to this interaction. If they change the Meta-Ruling, the Compendium ought to be updated, which is hard to accomplish if nobody knows the ruling except Japan.
The Hone Claws ruling has little bearing on the format, but is very ambiguous. Thus, it is a big deal, regardless of whether it will come up or not at a sanctioned event. It's a reversal of over 10 years of precedent and should be announced as such.
Also,
whenever the Constitution gets amended, it is a very big deal. While of course the 19th Amendment is more important, that shouldn't diminish the significance of the 27th Amendment. In over 200 years, we've only amended the Constitution 27 times (really 18 times, since the Bill of Rights was adopted all at once). Each and every one of those Amendments was a very big deal when it happened. As this reversal of a long-established Meta-Ruling ought to be.