Hmmm.......the "known good one" is exactly the same. Did learn there is another tab further up that the throttle picks up to operate the choke but the throttle only hits it about 1mm from the end of its travel and doesn't move the choke anywhere near enough to close it.
Salesman didn't know anything about it and the mechanic was away.
A smaller engine next to it with a different but similar carbureter/linkage set up was very definate in its choke operation.
Did also learn that any dealer can look at it under warranty and I don't have to return it to the online dealer I purchased it from in NSW.