I think you might be looking at a question that has no specific answer. LCSH has been around for more than 100 years and was assembled according to a process of literary warrant (heading by heading as needed) as opposed to universe of knowledge approach that would have tried to anticipate all possible subject areas. This means the ontology is organic and not always as consistent as we might like.
The most helpful statements will probably be found in the Subject Heading Manual H830 sheets. You can at least find a chronology of decisions that have been made over time with respect to the ways that catalogers have tried bringing out the geographic aspect of a topic.
From: Program for Cooperative Cataloging [mailto:[log in to unmask]]
On Behalf Of Jesse Lambertson
Sent: Friday, March 10, 2017 11:29 AM
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Subject: (may subdivide geographically) ?
I am looking at the Subjects Headings manual for information, a complete rule, on when a topic may be geographically subdivided and when it may not.
Cataloger's Desktop lists all the headings and includes the additional note about which ones may be subdivided geographically. It also mentions the addition of (May Subd Geog) as generated from the existence of "i" in field 008/06 in the authority record.
But I am looking for the rule that actually explains why some headings can be while others not.
In which documentation might I find this philosophical guidance?