Merging terms in a termset does not update site collections that use them

I have a farm with a termset that has countries of the world in it. We are merging some areas together, e.g. Antarctica is becoming part of Asia-Pacific.

I have tested this by merging terms in the "Place" termset, so "Antarctica" is merged with "Asia-Pacific" and "Antarctica" no longer exists.

In a publishing site collection I have a content type with a site column that binds onto the "Place" termset. The items in the site collection that used to refer to "Antarctica" now refer to "Asia-Pacific" when I edit the item (so I can actively change the term), however when viewing the item in a list and without making any changes, it is still listed as having "Antarctica" as the value for that term.

The mysite site collection has not updated at all. That has custom properties that also bind onto "Place" termset so employees can say where they work. If someone has "Antarctica" in their profile it still lists "Antarctica" in their profile even when I edit the profile.

I have tried running the Taxonomy hidden list update timer job manually, this does not push through the change.