Both the plug connectors and the transmission formats of digital signals are subject to significantly faster conversion than is the case for analogue interfaces. With the A2, we are assuming that the user wants to use the headphone amplifier for a long time and therefore believe that it makes more sense to only provide analogue inputs. Otherwise, the headphone amplifier may in some cases become impaired after a few years or it may no longer be possible to use it at all.
In addition, it has been our experience that many customers in the high-end sector have excellent transducer technology in stand-alone devices and therefore already have excellent high-level analogue signals in their playback chain.