It's actually a bit of the opposite. I'll try to explain.
GC6DK0D is so far of, that Project-GC's polygons doesn't apply. It is therefore stuck with the region defined at Geocaching.com. This region is "Brussels".
All other geocaches in Brussels are named "Bruxelles-Capitale - Brussel-Hoofdstad", because that is the local name, which then fits the other region names in the country.
The solution we will have to go through is then to actually move all "Bruxelles-Capitale - Brussel-Hoofdstad" into Brussels, even though that is less what we/you want. But it will then align better with the Geocaching.com data.
We will start this process today.