I’ve just recently purchased Amplifi TT ( Feb 2019) and was also puzzled as to why there was now mono out as such, Good news : It is Balanced to go into various interfaces/ inputs, I’ve plugged into a Mackie Mixer and bused directly to Logic ( Stereo) it sounds awesome. When I use AMP out it’s sound great also, but I do get lots of amp noise, depending on the Amp/FX settings and how close I am to getting interference. Direct L/R into Balanced inputs is the way to massively increase sound quality and levels, with a very low noise floor.