Slingload you've got it wrong.
ATSB has become an educational organisation. They seem to think that is their role not reporting facts. Not wearing lifejackets in this case had nothing to do with survivability in this case. The floatplane was still floating as most float equipped aircraft do when inverted. The issue is getting out of the aircraft unimpeded. With wearing a fully donned lifejacket as ATSB was trying to push, the chances of doing so are very much reduced. The Canadian report actually supports this if you analyse it carefully and take other factors such a hypothermia into account in cold canadian waters. In the case of the tassy accident that initially set the ATSB agenda, the plane was going to sink before it left the dock and the pilot did not instruct the pax to put their l/j on when it was obvious the plane was sinking. No mention of that 'fact' in the ATSB report. The simple view that to prevent a drowning you need to be wearing a lifejacket, while on the surface seems logical to the lay person, it ain't that simple.