I would agree that Trump should play no part in any inquiry. But regardless of who calls for it there needs to be an inquiry; an independent inquiry. Cut the Yanks out of it if that makes the CCP feel any better; the poor dears.
But that's the issue at the moment. Trump has called for the inquiry, Morrison's said "yeah, good idea", so it's Trump led. China won't entertain that idea in the slightest. Issue now is for any country that jumped on the back of Trump's call, like Australia, is that we've played our hand and wont be entertained.