Well I wouldn't expect them to make stuff up after we know it. I don't even know how that would begin to work. They designed a land they felt would fit well in Disneyland (whether it does is up for debate, but I think from the way they chose to blend it with surrounding lands, they did try and put some thought into that), and built stories for this new planet that were in part released before opening and others releasing next month.
As for Batuu's backstory, it's a planet at the edge of 'wild space' that used to be a central hub of travel for long journeys, but fell by the wayside when lightspeed travel was invented. These days, it's much more under the radar, which made it the perfect place for the Resistance to hide out while they regroup.