Of course this is correct if you being with a lossless file, but if you start with an already lossy file, despite it being possible to sound the same as a lossl

Of course this is correct if you being with a lossless file, but if you start with an already lossy file, despite it being possible to sound the same as a lossless file, when you re-encode it with a different encoding, for example ogg -> mp3, you'll lose different parts of the file in the compression algorithm, so it will end up sounding worse. I can't say I know how the different bluetooth audio codecs work of course.