I'd be wary of this and I will tell you for why.
I had an Indonesian bidder ask the same thing in June (after purchase). I refused and said they could have an immediate refund or I would ship with the full declared value. They wanted the items shipped, obviously hoping they wouldn't be stung for customs. In fact, they got quite a large customs bill. They refused to take delivery of the package; in fact, to-date the parcel is still in Indonesia customs. They did a 'transaction not authorised' chargeback with their card provider and now have a full refund of around 1800 USD. I still have no items back. Indonesian customs may or may not send them back to me and, if they do, I am responsible for return shipping costs so I will be out of pocket on two way shipping costs. Assuming I get the parcel back otherwise I am out the 1800 too.
I will now, never, ship to Asia again. UK, USA, Canada, Europe and Australia only for me.
So I think the question is the same both ways: if you under-declare and the parcel gets lost, are you happy to just write the money off? If you fully declare and the buyer refuses to accept delivery, are you happy to write the money off?
Or just apologise and block the bidder to be on the safe side. I know it's harsh but everything has shifted way too much in the buyer's favour these days and you've got to look out for yourself as a seller.