In this example, the two identification records were created 4 months ago and 7 days ago. Any number of independent comments (and/or other peoples’ IDs) could theoretically have been added during that interval. By collapsing the two ID events into one visual display, the sequence would be changed and become harder to interpret.
I do agree that this example represents a single ID, but only because the two names involved are nomenclatural synonyms that map to each other 1-to-1. But if this had been a split or a merge, instead of a swap, the mapping of taxa in old vs. new iNat taxonomy would be 1-to-many or many-to-1, and could not be considered the same ID.
So for example, if this had been a split of Yucca treculiana (s.l.) => Y. torreyi + Y treculiana (s.s.), the new and replaced ID records could not be said to represent the same ID.
BTW I do still wish this proposed change would be implemented for taxon change IDs:
https://forum.inaturalist.org/t/improve-wording-of-ids-created-by-taxon-changes/3705
Actually I’m referring back to the concept you originally stated as
My assumption is that this whole discussion is predicated on allowing an iNaturalist user to track and filter observations using different taxonomy (and taxonomic concepts) than the “official” iNat taxonomy. So if one of my two examples above represents the user’s preferred taxonomy, and the other is iNat’s current taxonomy, they are indeed two different taxonomies that do not agree. Depending on the direction in which you are trying to reconcile the two taxonomies, it is either a 1-to-many problem
Y. treculiana (s.l.) => Y. treculiana (s.s.) + Y. torreyi
or a many-to-1 problem
Y. treculiana (s.s.) + Y. torreyi => Y. treculiana (s.l.)
I know you understand what I am saying here, so I must still be missing some other concept that you are trying to convey when you say that those two different names (and the concepts they reflect) are in agreement.