I am sorry Katzsky but you are just playing with semantics. To put it very simply; if you send a redbook 16/44.1 file to Bartok or Rossini the sample rate will be changed (upsampled) to DSD64 or DSD128. Those two options are what the manual refers to as optional 1-bit upsampling ( my emphasis and this is for PCM sources, ). If those options are not selected then there is default PCM upsampling implemented; to 24/352800 ( DXD). In short , speaking figuratively, you cannot put 16/44.1 in and get 16/44.1 out. With Vivaldi you can do this as it can be used without an upsampler or be set to Clone Mode.
Upsampling is a form of data conversion and differs in intent from the upsampling used as part of the Ring DAC process;
All dCS DACs do use an upsampling process as part of the way that Ring DAC works. All incoming data is upsampled to 706.8kHz or 768kHz as this is how it is fed to the 5 bit modulator as the mapping process ( how the data is distributed to the current sources) is 5 bit. However this differs from an upsampler as the resulting output from the DAC is not converted to another sample rate. 16/44.1 goes in, there is some processing which includes upsampling and, again figuratively, 16/44.1 comes out. I say figuratively as what actually comes out is an analogue signal. I have been careful to differentiate the two when writing about my particular misgivings about the sonic results, as I hear them, when selecting upsampling in contrast to no upsampling :