I would agree with Gordon that RRS13 does not define "tacking".  "Tacking" is used in the titles for both RRS13 and RR18.3  and  each rule appears to place a different meaning on the term "tacking".
The MR Call Book "is authoritative for umpired match racing only", meaning it is not authoritative for other disciplines.

From Miriam Webster :
noun (1)
c: a change when close-hauled from the starboard to the port tack or vice versa

intransitive verb
1

a: to tack a sailing ship
b of a ship: to change to an opposite tack by turning the bow to the wind

transitive verb
4: to change the direction of (a sailing ship) when sailing close-hauled by turning the bow to the wind and shifting the sails so as to fall off on the other side at about the same angle as before

To answer John's question, (" can tacking have a different meaning or scope when used in different rules"),  we would have to decide whether the rule uses the term as a noun, intransitive verb or transitive verb.

I believe RRS20 uses tack as a verb.  A boat hails for room to do something.
RRS44 uses tack as a noun.  the rule names a tack and gybe.

Michael - Unfortunately, in the fleet racing rules, we don't have the concept of last point of certainty as a general concept.  It does appear in 18.2(e) but not in general.

Suppose Blue was clear ahead before she bore off to this course, perhaps because she went around a mark.  Yes, they would be on different legs, but probably sailing their proper courses, so no RRS 23.2.

Which will convince me better that you were anxious.

"I hailed Starboard. They ignored me. I hailed louder again shouting you need to tack too. They ignored me. I altered course"

"I wasn't sure if they saw me and I was anxious so I altered course"

Can you expand on this?

John, I am glad that the WASZP rules are working in practice.  I think that the wingfoils will go a different direction, with little or no limitations, at least in part because they are always in the standing position.  I think that should be up to the fleet decide and adopt in their class rules so we shall see as the class matures.