"This is not the eastern, but the southern hemisphere."
Translation:Dit is niet het oostelijk, maar het zuidelijk halfrond.
Where did you find oostelijke on taaladvies? I can only find oostelijk. And I would go by taaladvies over Vandale since they (the language institute) actually have a say in things and the power to change the rules. Vandale is just an observer.
I'm dutch and het oostelijk halfrond definitely how the term goes. Because this isn't a description but a fixed expression.
In any other case it would indeed be oostenlijke. Ask her if she thinks it is het openbare vervoer too. Another fixed term which according to normal rule should need an e. (But actually always is openbaar vervoer)
Same question voor "het centraal station" Does she call it centrale? (Which actually is possible but not just as the name/term for the station but if you are describing it's position in a city compared to another station. Not a phrase you would really use in the netherlands)
It concerns fixed expressions.
So an adjective and noun which are only ever used as a fixed pair. Nearly like a compound without being a compound.
So when the adjective isn't really describing it anymore but is an integral part of the word/term
Like het "centraal station" nobody even really think about the word central anymore the two are almost experienced as a single word.
There arent many of these (exceptions) btw.
Het koninklijk huis is another one. (The royal house, not meaning the residence but as in the house of... The royal lineage)
You don't really need to worry about these exceptions.
.. maar het is het zuidelijk halfrond.
But in dutch that doesn't flow well and imo it doesn't flow in english either unless you allready said hemisphere in the first half.
Since Southern hemisphere etc are fixed expressions it is weird to put a lot of stuff in the middle (for lack of a better term) before you reach the actual second half of the term.
(So imo your way makes it make less sense)