Earlier quoted context omitted.
The other way around. There are 7 notes and the accidentals give us a 12-tone chromatic scale.
Is this a cultural thing? I was always taught there are 12 notes, while any standard scale contains only 7 of them. (The chromatic scale obviously being the exception which contains all 12.) Accidentals are just for notation -- obviously B-flat and A-sharp are the same "note", just as F-sharp-sharp and G are. Our entire turning of equal temperament is based on 12 equal intervals, not 7. So I'd argue parent commenter…
So...one could argue for either or both interpretation and explanation. The note names, sharps and flats, is what is most arbitrary about it.