I am not sure in Portuguese (still learning!) but in other Romance Languages, as in English, there is a difference between "nice" (e.g., simpatico/amable) and "good" (e.g., bueno/buono). A man may be fundamentally "good" in that he cares about his family, provides for them, and has their best interests at heart, but that does not necessarily mean he is nice. For example:
"My husband has difficulty expressing his feelings or showing the children he loves them, but he is a good man."
Again, I don't know if this holds true in Portuguese, but that might be the issue.
as a natural-born English speaker, if 'good man' is an acceptable translation, then i think 'nice' wud be synonymous with 'good'. i'm only a learner of Portugues, but i'v spoken English for over 40 years as a natural speaker, & i can't think of any time that 'nice' and 'good' are not acceptable synonyms. i'd report it if i were you. they probly just need to add your 'nice' translation as one of the acceptable answers.