As the audio is now passing through without local processing that sounds entirely correct operation. The sound mode task moves from the TV to the receiver or bar.
I just got a soundbar the LG LAS454B, i also recently bought a LG LF6000. I was connecting the two yesterday and noticed something strange, when i set audio output to either sound sync or external it locks off all the other audio control options like sound mode and such. I also see there is a DRC button but you need to enable dolby digital which im not sure if i can with the audio settings disabled? Any tips are welcome here guys!