CASA don't investigate anything, ATSB do. CASA may make enquiries afterwards, but who knows where that would lead as they have no piston knowledge anyway if some of the reports in the last 10 or so years are anything to go by.
The Jab engine probably has a higher rate of destruction than others, but they do a lot of hours too.
And keep in perspective the one last week ran out of fuel allegedly. Hardly the engines fault.
Many problems seen in RAAus could be attributed to owner maintenance. And possibly the ones in schools with qualified maintenance too. Who knows.
MIHC has raised a point the heat transfer of the machined head may not be quite as good as the cast surface too, but I have a feeling it is more about airflow.
Airflow under a cowl does not do what you think it does. It defies simple logic and until you measure it and video it you tend to believe what looks like common sense. And it is very challenging when you see results that are the polar opposite.
For more info get the October AOPA magazine or the September Airsport Magazine, a great article in there.