Whats your point exactly? That they did not have clearly defined borders with a map? That they dont have clearly defined property borders? Where do you base these assumptions on?
In dnd they do have armies who maintain there borders and border conflict happens all the time. Some nations are marred with borders conflicts between them and their neighbours. One region's basic premise (border kingdoms) is that its borders basicly change by the day. Why would that make the region special if it happened everywhere?
Agree that Kahga's situation is silly. But borders have nothing to do with it
Kahga is a nativist in this story but is perfectly okay with her racially diverse circle of druids, for some reason Tieflings is where she draws the line. As someone else pointed out in this thread her focus should be on exterminating the enemies of nature in goblins and Tieflings both, which should be communicated clearly. What does Kahga do right now? Call a demon child a parasite, kill it, cringe and speech about "protecting her people".
Where borders (don't) come in is that Larian has essentially created the only possible scenario in this area where there is a group of people who want another group of people to get out of their land. The problem is that this land is really a big house that they were not really using anyway, the other group of people is defending it themselves and the immediate solution that is on the table is mass murder for some reason. The amount of hoops you have to jump through to put a racism allegory into a medieval fantasy setting while also presenting an as diverse and harmonious society as possible is truly staggering.