In September 2013 Watch Dogs was classified at MA15+ by the Australian Classification Board but now, after the extended delay, Ubisoft has paid the board to reclassify the game and the classification has been changed to R18+.
Why? At this point in time we only have the information on the Classification Board's website to go on. It seems like Watch Dogs has been changed to R18+ as a result of 'high impact' violence. This might be a result of additional content, or it could be inconsistency on the Board's part. At this point we simply don't know.
We don't know because Ubisoft has asked the Classification Board to withhold releasing the report until 17 March for "commercial reasons".
We also got in contact with Ubisoft locally regarding the change in classification, and we hope to have additional information, in the form of an official statement, overnight.
Commercial reasons could mean that the violent content is related to something new Ubisoft wants to roll out in a more controlled PR driven manner. It could be related to some sort of plot spoiler. Nevertheless, we won't know until Ubisoft tell us, or until 17 March when the report is made available.