I do think it is not changing in the minimap because in this trigger, it replaces a tile and so the minimap cannot detect it because it only happens in-game, it is only there where it changes the tiles and so the minimap in WE or World Editor does not change because the changes to the tiles are not taking place yet.
This is my answer if you are referring to the minimap in WE but I really do know changing or replacing tiles through trigger doesnt change a minimap's appearance and only through manual changing of tiles.
Though I might be wrong also.