For the addon dev: Same happens with other minimap addons, like Votan's Minimap.

I think I found the functions in WorldMap manager adding that headers:
function WORLD_MAP_MANAGER:TryShowSpectacleMapHeader()
Calling WORLD_MAP_MANAGER:ClearMapHeader() should clear and hide the header afai can see

Found in ESOUI code at \esoui\ingame\map\worldmap.lua
function ZO_WorldMapManager:TryShowSpectacleMapHeader()

ZO_PreHook(WORLD_MAP_MANAGER, "TryShowSpectacleMapHeader", function()
   --Votan's Minimap uses a dedicated mapmode (MAP_MODE_VOTANS_MINIMAP) to show the minimap is used. If we ask for that being active we can detect it's the minimap addon showing, and not the normal worldmap. 
--Other addons like MapPins and Fyrakin's Minimap hopefully got such dedicated MapModes themselves  !!!

   if WORLD_MAP_MANAGER:IsInMode(MAP_MODE_VOTANS_MINIMAP) then
     WORLD_MAP_MANAGER:ClearMapHeader()
     return true --supress calling original code
   end
  return false --call original code
end)

this is untested and maybe not working, but pass it on to the addon devs, maybe they can have a look at ZOs code and prevent it from showing at their minimaps that way.