As part of the AQIS requirements for entry into Australia the dunnage (outer packaging and pallets) are required to be treated through one of many treatment options before they are cleared to enter Australia. This can occur either before being shipped in their source country or once they arrive in Australia.
So yes, they have been treated but ... our soap nuts are packed in sealed packaging and the cardboard chests that they are packed in is also lined with a biodegradable liner. The treatment used for our soap nuts is methyl bromide which is also known for not leaving residue after the completion of the treatment process.
"8. Containers, timber packing, pallets or dunnage associated with the consignment will be subject to inspection and treatment on arrival, unless certified as having been treated by an AQIS approved method. (Refer to the AQIS publication ‘Cargo Containers: Quarantine aspects and procedures’)."