Well that says it all and it seems you did read it after all and even in Italian
(corrisponde a foto da 12 megapixel).
That you presumed to be able to extract 48MPx from that was an error on your part, although I understand the problem when the camera is advertised as 48MP, many people will think that is pixels i.e. what they can get out.
Unless you see a post from Fairphone i.e. with an [F] at the bottom right of the avatar then the posts are from users.
Clearly it would be nice if Fairphone and other’s clarify this by using the term MPs for the camera sensor array and only use MPx for screen array.
MP > Mega Pixels and Mega Photosites
However this is a quad-bayer from Samsung and if you had read up on what you were buying, as it seems so important, then you would not be complaining.
The title of this topic can be misunderstood as the read camera is both 12MP and 48MP but for the technical person that’s 12MPx from 48MPs