Question If the digital audio coming into the BMC-2 is at 24bit / 96kHz, there is no downsampling or upsampling I am concerned that the "Internal Sample Rate (fallback): 48kHz" means that the audio is then being downsampled to 48kHz and the upsampled to 96kHz

There is no sample rate converter in the BMC2. The audio is handled 100% synchronously (all incoming audio samples are going to the DAC after the volume control) with extreme jitter reduction before the DAC no matter what sample rate you send to it. The fallback at 48kHz is the rate the BMC2 wakes up at when no audio is sent to it, We do this because some digital devices and digital speakers might be sensitive to start-up and source/rate switching etc.  We have taken a great deal of care when switching between sources, switching sample rate etc., so that there is an absolute minimum amount of glitching going to these devices and speakers.