Thanks Roger. I thought the same thing when I first saw it; indeed, Fischer was still using descriptive in 1992 (http://www.chesshistory.com/winter/extra/fischergligoric.html
A letter on the CB article from the son of the tournament organiser says "A book containing all matches from Hercegnovi tournament was published and if I remember correctly, Bobby was paid two million Yugoslav Dinars for his part."
Meanwhile Chessgames has a number of Fischer's games from this tournament annotated by him (see http://www.chessgames.com/perl/chess.pl?annotatedby=19233
) and the Korchnoi-Fischer game at least matches exactly, so I assume the aforementioned tournament book is their source.
Also note that the game scores are very neat by Fischer's standards - even in slowplay games his writing is almost impossible to read by the end (another example: http://blog.chess.com/qixel/famous-score-sheets2
) so I would guess that he recorded the games, quite possibly in descriptive, deciphered his scoresheets (something no-one else has managed to do, judging by the Winter article!
) then wrote them up relatively clearly in algebraic later with notes, and gave that to the organiser for the book.