According to Chambers, Fibonacci - dextrorse did mean that formerly but is now taken to mean the opposite - ie turning to the left. This was a clue in the Daily Telegraph's general knowledge crossword on Saturday and the answer there was sinistrorse as given by valerieb1254 - though owlandpuss is now too late to get their entry in as the closing date for entries is today.
Quite how the two words - dextrorse and sinistrorse - are now taken to mean the exact opposite of their derivation I find difficult to fathom, so I can certainly understand where you answer came from Fibonacci. Perhaps someone with green fingers can explain.