I just got off the phone with fairphone and got basically the same reply.
To answer your question: no, the phone is not up to date due to the fact that I did not took the time yet to figure out how the updated version can be rooted afterwards.
According to the support worker he’ll send some more information a my mail-address and I might need to switch from Fairphone OS to the open OS version.
I could definitely see small changes in the display layout on the back of the spare part, so the explanation seems reasonable to me.
As mentioned: I am limited by keeping the OS rooted and depend on keeping that functionality available. I will therefore need to look into the issue, try to either update the current version and root it afterwards or switch over to the open os, import the missing packages and see if that works.