There's noway for the 7623 to know what the audio format is if the info frame says 'refer to stream header'.
DIS_I2S_ZERO_COMPR controls the I2S output depending on compression. Also MUTE_AUDIO can force an audio mute. I'm not sure what you are writing to 0x03
Check out the various control fiedls listed inthe hardware guide section 5.31.1.3