According to the Ch.7 video he crashed out of the scenic flight phase a few Km North of his departure point and was not taking off or landing. In the absence of a mechanical failure the next thing that ATSB should consider is the post stall instability of float aircraft and how pilots are trained to deal with it.
An inherent problem is the floats providing lift
after the wings stall, or better still
a float providing lift after
a wing stalls. This does not seem to have been considered in the (usually) Canadian crash reports, with their emphasis being the lack of stall warning. Who's tried a power on 60 degree turning stall in a DHC-2 Beaver ? I have in a float M7 Maule, and although I kept the thing balanced the result was a nice flick roll entry (80 degrees) into an incip spin (at 6000'), which was a lesson not to be forgotten.
Sky9, that seems to describe stall characteristics for the landplane version ? There is more at para 1.10 in
Transportation Safety Board of Canada - Aviation Investigation Report A09P0397 that expands on this. Also a turning accelerated stall in any case will have higher pitch/roll/yaw rates than with wings level at 1.0 Gz, in this case perhaps too much to recover from.