This is because we pass in InstanceIDs (PKs of Map table) to TomTom:SetWaypoint's map param, instead of UiMapIDs (PKs of UiMap).

It seems the UiMapAssignment table maps InstanceIDs to corresponding UiMapIDs, so probably we want to use that instead. It looks like a join table; can one InstanceID have many UiMapIDs or vice versa?

If we can get the UiMapIDs reliably, then we only need to store this in the final locations lua file.

https://wowpedia.fandom.com/wiki/API_C_MapExplorationInfo.GetExploredAreaIDsAtPosition
gets called by
https://github.com/Gethe/wow-ui-source/blob/53eff055dcffff98029f0438f9b0da421e4dad70/Interface/FrameXML/MapUtil.lua#L62
in order to get the best (explored) area for the mouse position.

It seems it actually maps PKs of AreaTable to PKs of UiMap, which throws a wrench in the works. AreaPOI is the only dataset which actually provides this information, and I'm not entirely sure I can just replace the uiMapId I get from C_Map.GetMapPosFromWorldPos directly without also transforming the mapPosition I get from it somehow.

Needs further research.