Of course you are right but in this case we have a survivor clearly saying there was an electrical failure and the pilot decided to ditch voluntarily.
It could be the usual crappy press reporting but it doesn't quite sound like that to me in this case.
Until the survivor comes out with a clear report, we won't be any wiser, but until then it just seems almost totally bizzare.
I say "almost" because I have met PPL holders who thought that a VP prop is implemented with a variable ratio gearbox. Similarly there are loads of DA40TDi / DA42TDi pilots flying who know zilch about the systems involved, etc. It is not totally unbelievable that this pilot decided to ditch in the belief that his engine would stop at any moment.
The converse is that he had an engine problem causing the forced landing, but in that case why not make a radio call? The probability of an engine problem and a concurrent radio failure is absolutely miniscule.