Carnet - Stamp required before leaving home country

[StepThruPanAm]

Hey guys,

My partner and I have been living in Australia for the last 2 years and are embarking on a trip through SEA etc shortly. We filled in our Carnet application but delayed sending it off in the hope of getting as much time out of it as possible. We boxed our bikes and left them with the shippers who have now told us we require an Australia customs stamp on the Carnet before the boat leaves?
This was not the info we were initially given. I spoke with Customs who agreed a stamp would be required before the boat leaves but we are down to a few days now and it doesn't seem that this will be possible if if we fasttrack the Carnet. Does anyone have any similar experience? I can't quite understand why we'd need a stamp before the boat leaves, rather than just before we pick up the bikes in KL?