That's because there is no profile for that, as per the spec the hands free profile only supports Mono This changes with LE Audio (spec released in March iirc)

That's because there is no profile for that, as per the spec the hands free profile only supports Mono This changes with LE Audio (spec released in March iirc) which is much more channel oriented (e.g. 2 channels stereo playback + 2 more stereo microphone), has a new codec (LC3) and has support in the upcoming android release