In balanced designs it is appropriate to sum the two signals into one and then split them again, at various points in the chain. This is how noise is cancelled by using balanced circuits, and it is a misconception that a fully balanced system keeps the in-phase signal separate from the out-of-phase signal throughout the audio chain. Splitting and recombining is part of the process and can be seen in top of the line Pro gear, as in domestic audio gear. It is true that some equipment is entirely single-ended and merely uses an inverter to split at the output to provide a balanced interface for cables. This is not inappropriate. Yes, it means there are no benefits of balanced operation within the component, and yes there is an added active stage on one leg at least, but having balanced drive on the cables can have its benefits. There is no simple and single right way to use balanced topologies.