is it still true that there has never been a pilot survive a ditching into Bass Strait?
No, not true.
One of two pilots survived a ditching on an Aero Commander (not sure of the year, mid 80's possibly) but was not able to be rescued despite being found floating alive by an AN F50. The rescue effort was an absolute shambles, a blight on the SAR arrangements at the time, and a bloke died where he shouldn't have. The ABC did a good doco on it called "Search without Rescue" - well worth a look.