Yeah seems to be normal.
from the FP website:
Q: What does “48MP (12MP output)” mean?
A: The raw sensor (the Samsung GM1) is 48MP. The primary focus of this sensor is to gather more light and therefore perform better in low light conditions and capture more details. This is achieved by combining tiny pixels of 0.8-micro to deliver light sensitivity equal to 1.6-micro pixels. Hence its effective output is still 12MP. This is common practice in the industry with phones such as the Samsung S5KGM1, Samsung Galaxy A90 5G, Nokia 7.2, and the Sony IMX363.
and on the forum there are also some topics regarding this:
https://forum.fairphone.com/t/fp3-new-camera-module-still-generating-12-mp-pictures/64573/5 and https://forum.fairphone.com/t/old-and-new-camera-photo-comparison/64727
I really don’t know… I always apply them one by one