I was about to ask where you found
界界 as the kanji.
The singular kanji meaning is to “separate”
or be “between X”.
So there might be some meaning to it,
just nothing substantial or concrete enough.
Or blame AT and Toyo for ruining character
arcs of DBZ characters from the past.
tbh yes, Bulma should’ve just made a space ship to travel to new namek, and it’s convenient that they didn’t know where it was.