When learning a language, you don’t do literally everything by the book. In the real world you have to figure it out and extrapolate from incomplete information, and sometimes you get it a bit wrong.

From a few minutes playing on an autotranslator, it appears that Norwegan uses the same word for male/man and female/woman. Like the noun and adjective versions are the same word with different conjugations. A Norwegan learning english as a second language can quite reasonably be unaware that there is a distinction there.