is 320kbps a lie?

So the online youtube downloaders always give you the option of 320kbps for audio conversion but apparently the bitrate of youtube auido ranges from 48kbps to 256kbps maximum and I just downloaded a video with the --audio-quality 0 and -f bestaudio commands and the audio bitrate was 249kbps. So is 320kbps bitrate a lie when it comes to youtube downloaders? Does it just take up more file space without having better quality?