Why don't all scenery addons show in world map and as POIs?

As per question above: why do some addon sceneries show on the world map and as POIs in game and others don’t?
This one for instance: Cinque Terre, Liguria, Italy for Microsoft Flight Simulator | MSFS
I can clearly see it at work when I fly over but there are no POIs shown, as opposed to this one: Italy - Porto Venere for Microsoft Flight Simulator | MSFS which shows in map, POI and it’s clearly working.
The list can go on… Matterhorn for Microsoft Flight Simulator | MSFS does not show in the map or as POI (but I can see the different textures when I fly over), but this one does show: Italy - Sassolungo for Microsoft Flight Simulator | MSFS

Am I doing something wrong or is there something coded into the addons that does make them not show up in the map? Can I do something about it perhaps changing a couple of lines of code?
Thanks!