Actually, I'm not convinced it is a simple case of a lossless file + the compressed version bolted onto each. This is because normally, the file size difference between say a 64kps file and a 256kps file for a typical 4min track is more than 2mb (which is the file size difference of the respective lossless files). Moreover, when you transfer to a HiMD device, then the transferred, compressed file, remains in the optimised folder, suggesting that a conversion process has taken place. Therefore, I suspect that the lossless file is just that, but the various implementations of the lossless files have additional information to optimise the conversion process for their respective bit rate.