They do physically exist. You can even see pictures of the physical buildings their offices are located at on this very website.
I would hazard a guess and say that being a video game development studio... They probably don't get a ton of physical mail. Thus don't have a particularly notable set up. (I mean looking at their office in gent, they just have a dinky little mailbox on the corner of their building)
Literally you can look at the building on google street view.
With the address of Opgeëistenlaan 2, 9000 Gent, Belgium
But again, I don't know what their set up is to receive physical mail.
Also, you can never count out the uselessness of delivery services... They often will just not bother actually delivering things...
