It appears that the RS130 cannot take a PCM file and output it to DSD. Perhaps in Roon selecting HQPlayer which can perform a PCM to DSD file conversion, can then output to a DSD DAC?
I attempted this, but it does not work, as you cannot pass through Roon with HQPlayer. When using the 2 together, HQPlayer ends up being the output, like the RS130 is an output. Hope you find a work-around, as I wanted to do this as well.
The answer to the title of your post is that some connections/devices cannot provide native DSD so it is transmitting DSD over a PCM carrier signal. No idea if that is frowned upon/inferior, as I’ve never tried it. I don’t think it is what you are looking for though
You can also let Roon itself (without HQPlayer) let PCM resample to DSD (until DSD512, if the used DAC will support this). But here no DSDx48 is supported.
DSD over PCM means, that here DSD will encapseled into PCM.
For DSD64, the DAC must support at least PCM 176.4, for DSD128 → PCM 352.8, for DSD256 → PCM 705.6…
This is needed for systems, where the RS130 don’t know somerhing about the native DSD capability of the DAC, which depends on the DAC and the used kernel in the RS130.
Normally Roon will show you, what it’s possible to set.
Here for my RS150 on a Holo Audio Cyan2:
So I can set here the Roon upsampling to DSD512 native (no DoP, but native).
If DoP is properly implemented, there should be no difference in SQ between it and native DSD.