I think it traces back to the early WEG days. WEG provided the very backbone, the foundation, for everything we know about the Star Wars universe outside of the films.

They did a lot of awesome work expanding the universe BUT there was one aspect of it that was eventually abandoned but the echoes of which could still be felt going forward. That aspect being that the original contention was that most of the galaxy was still unexplored and it was new founded Empire that was leading this charge to explore what was out there and to conquer, exploit and enslave anything and everyone they came across.

For the longest time, it was a fact that Mon Cala/Dac was a newly discovered planet within the OT timeframe.

So with that context in mind, the Unknown Regions being laid out as they were made some sense. But it should have been readdressed loooooooong ago. That they’ve not done so at this opportune moment in time with the new canon is a massive failure on their part.