seen this and wondered what everyone makes of it?
I feel vaguely embarrassed for the national government that would write these missives in the form presented. No mention of the legal process being undertaken or the definition/limits of authority, no reference to variations in regulatory responsibility associated with different airworthiness or certification categories, no mention of a proposed airworthiness directive, or specific technical problems, specific engine types, research that's been undertaken or anything that would lead one to confidence. It looks like government gossip inviting public gossip, in the service of arbitrary power, wielded by petty bureaucrats.
Before government takes public action to sully the reputation of private tax-paying companies and reduce the value of private property its generally considered a good idea that they have some technically documented basis for doing so. Their action should be backed up by specific legal authority, and include a data-backed, defensible proposal on which the public can comment based on the detailed facts presented. I'm certainly glad that CASA has no influence on me, and to a lesser extent glad that I don't own or otherwise have a stake in Jabiru products that are falling victim to CASA's apparent amateurism.