Let me correct you here, you wrote “LTL shipping requires a ‘Bill of Lading’ (BOL) to be produced via SellerCentral then the Trucking company has to make an appointment at the FBA Fulfilment Centre to deliver the goods. I don’t think either of those things could be done while the goods are still in China.”
The Bill of Lading is product via SellerCentral only if you use Amazon’s trucking service, and about the appointment the trucking company will make the appointment with Amazon once the goods arrives at the port, so once the goods arrives at the port the trucking company will ask you for the Amazon reference and shipment ID, they will then create the BOL and schedule the pick up.
So yes you can ship pallets straight from China to Amazon just make sure with your supplier that they correctly put the carton and pallet labels (ask for photos) and that they use strong boxes.
Its something I did years back so I don’t know if anything changed.