Mono stream audio reproduced only on FL speakers

when one channel is configured, audio is being reproduced only on the FL speakers, the expectation is that with a mono stream audio should be reproduced on both FL and FR. this can be tested with tone.rs example, if 1 channel is configured the audio is only played on FL. tone.rs is the rust implementation of tutorial4.c in pipewire. Testing tutorial4.c with 1 channel the audio is being reproduced on both FL and FR.