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Lots of manhwa use the same generic architectural designs (it will be too time consuming and tough for the artist otherwise) and TBH architectural designs are harder to draw so artists tend to reuse generic and ready made designs.

If you've red a lot of Manhwa you'll notice majority of them have the same bedrooms (the one which is black/white and have a deer head design at the top of the wall in the headboard of their bed)

Also the big penthouse with a second floor and a chandelier which is circular in desig

In Medieval/Nobility era they all have the same design for the Palace (the one which has a like a bridge at the top) also the same garden design outside all Duke's palaces HAHAHAHHA

Hope that helps!