I doubt that this is a pure amber vs. byzantium issue (I reckon that if you were running amber on your L13 you would also see the HDMI profiles). However the audio on the L5 in byzantium might have more options of course - is there anyone here who can check? If not, we could ping one or two of the devs who hang out on these forums.
@amosbatto was asking a related question here: L5 Multiple Audio Outputs.