Well, the addon's old source was pulling from the server, correct. Via DoesGuildHistoryCategoryHaveMoreEvents etc.
I did not check yur new code bu if you did no remove this and did not change the SV data so that LibHistoire's SV is used instead, nothing changed
This needs to be stripped and totally re-coded to ONLY use LibHistoire as the source.
Never worked with that lib but the description got the "For Developers" and "API" section.
There also are examples how to iterate over the stored events of the lib, so you could fully stip the event collection AND storage in the addon's own SV data, and just switch to use LibHistoire instead.