It really doesn’t, assuming you package and label the bike as required by the DG Regs (I used to be a DG Shipper specialising in Lithium batteries, so I have a vague idea of what I’m talking about...). You are either shipping lithium batteries, or lithium batteries contained in equipment. Either way, the Wh rating of the battery exceeds the limit for air transportation under IATA regs.
I suspect one of the reasons they want the whole bike back is because it disguises the fact there’s a (potentially faulty, so should not be shipped. At all. ) battery in the box.