No, you didn’t miss anything. It is a question asked a few times before, with a complex answer.
While I don’t entirely disagree with your expectation, there are reasons why autocomplete is only linked to the GEDCOM PLAC data (wt_places table) not the Google Maps data (wt_placelocations).
- Not everyone use the Google Maps module, so at the very least the code would need to identify that.
- Among those who have it enabled, many still don’t really use it, so have many places missing.
- The GEDCOM data is specific to a single family tree, but the GM table is site-wide. It has no tree identifier attached. So a single place might have multiple different spellings, depending on the tree it came from. That could be very confusing for users.
- The GM module is secondary to the GEDCOM data. The GEDCOM should be correct first, then the GM data can be created properly to match and supply coordinates.
I’m sure some of these points could be changed (fixed), but it was always planned that the entire place-handling code would be re-written, though little progress was ever made. It is a VERY complex area.