Because MIJ bodies made out of Tilia Japonica(Japanese Lime) are allready called basswood guitar bodies, or whatever hybrid those japanes grow commercially.
Its simple really, same types of woods but due to their origin are called different. Think ash vs swamp ash vs sen or maple vs hard maple or mahagony vs korina vs nato vs agathis or australian blackwood vs hawaian koa, endless list really.
And i think, not sure though, in the USA basswood has a bit of a negative ring to it and american linden probably sound much more exclusive i guess....