Outlandish claims you say? Well then, explain how we got the map in the first place? Maybe Thargoids gave it to us? Or Guardians? Yeah, roight... It was the probes, millions of them.... And yes, their probes with their tiny telescopes were able to spot the brown dwarf by using GRASPADIS array (gravitational space distortion sensors)... Swarm of probes is linked and creates an array that measures spacetime distortions to detect objects that are not visible to any other sensors.... This is also how we are detecting small black holes... But let me guess, you will also deny this, roight?
Yes, because that's literally pure technobabble gibberish that you just made up. There's no in-game explanation for the galaxy map that makes sense or even works, period. That's why it's a problem in that sense.
Like I said, I'm fine with the game development reasons for it. But let's not pretend that there's any logical reason for it to exist in the setting, because there really isn't.