The RE agent escalated this rather than picking, correctly: folding centre into L/R changes how dialogue sits against the music, which is an aesthetic judgement about the game and not a container detail. Decided: explicit ITU fold, centre at -3 dB, recorded in the manifest with the rest of the transcode command. Pinned rather than defaulted because a default is a decision nobody made -- invisible in the output and free to change between ffmpeg versions.