A37575 - just a quick point. I used to work for that operator.
Yes, training was provided.
Yes we had access to the throttle at all times via the front seat when starting.
Yes passengers were briefed on what not to touch.
Yes we didn't use chocks because on the grass the tiger needed about 1500 RPM to start moving.
And Yes we had a written exemption from CASA to start the aircraft in that fashion.
I don't fly for them any more, but from my 15 years in the industry, the operation was no more unsafe than anywhere else I've worked.