We will see, I certainly will keep you in the loop

I once had a similar problem with importing a digger to NI. It needed steralising and then a cert from a vet.

I was fairly sure I had mentioned it: https://forums.motorhomefacts.com/78...ml#post3092673

Yes you did mention it, however I had it in writing by the forwarding company that it was not required. According to the Australian custom department fumigation only needs to be done between September and May.
Some shipping lines However want it done
Regardless to limit the risk if a bug is found , the whole ship has to sail to Singapore to be fumigated.
The line we using now NYK is obviously willing to take the risk

Is it the line that's taking the risk, or Australia?

Good question, I suspect that If a bug is found and the ship is refused entry and gets diverted to singapore for fumigation some financial damage is carried by the shipping line. However I heard that in this case the costs are getting divided between all the Senders of goods. I have read that’s according to international law.
If there is a bug and it’s not found things get pretty bad for the country.