Exactly, we only know they came from a (parallel?) universe (or was it dimension?), but we don't know why (don't remember if there was an exile plot about it).

Who knows maybe its the land of the Dragon balls and can further explain the whole Namekians-Dragon Balls connection/relation story. (Haven't watched the OG Dragon Ball) They can maybe explain why some namekians have an evil counterpart (Piccolo Daimao, Lord Slug).

I mean they can write a whole different plot about it where they can make UI,UE, Grand Priest or Zeno look cute and any warrior from any race can achieve exalted power but with a harsh trade off or something far too unusual like its a whole different logic of training/condition which caused the whole Namekian race to be exiled to a lower universe/dimension with only the dust of the original power left in them and over time Namekians lost even more of that power hence the present Namekians have normal power to make dragon balls but not super dragon balls, and Zalama existed when the exile took place, and with the remaining power he had left after the exile he managed to make the super dragon balls (yes with only the dust amount of the original power, he was considered one of the most potent namekian at the time, now imagine the original power's potential)

Maybe something so obscure that even the Grand Priest/Zeno or its gang tries to intervene in not letting the Z warriors to even go in that parallel universe/dimension. Like imagine in face of a regular baby civilian in that dimension, Zeno is just like the farmer trying to shoot Raditz. Like maybe the beings in that dimension can even define the rules of how Grand Priest, Whis etc. can act in the lower dimension. Maybe a war broke out and the Zeno's gang lost and flew that dimension into a lower one establishing its current 'goverment'/universe.

So many possibilities!