Hmm, not sure mate. I see this is not listed on CDON yet and they usually get the listings up early but I don't think this is a Platekompaniet exclusive as they rarely have steel exclusives. Have to wait and see.
It's unlikely that a moderately successful US horror film would get a steelbook release only in one Nordic country, but of course it's possible.
Some recent Nordic-only releases: Villmark 2 (a Norwegian film, aka Dark Woods 2 or Villmark Asylum) got a Nordic four-country steelbook release in 2015. On the other hand, Tuntematon Sotilas (a Finnish film, aka Unknown Soldier) got only a Finnish steelbook release in 2018.
But Brightburn steelbook releases have already been announced at least in the UK, Czech Republic and India (looking at HDN release threads); my guess is that there will be more