It seems like it simply took a while to update (or for Apple to sort out the back-end).On my iPad the region is shown as unknown but on my iPhone it is shown as BE.
Mine now shows as "CH", which is where I live (and which network provider I'm using) and isn't where my Apple ID is set to.
I switched to another e-sim (to a different country), rebooted, and the phone still shows as being in region CH.