[...] But this hasn't been confirmed (nor denied) by RME [...]
To be very honest .. you expect a bit much. Do you know any company discussing product design
or details of their implementation in the public (which is surely part of their intellectual property) ?
RME is already very open in communication. See alone the technical data of their products in the manuals or on the Web.
The documentation of the competitors is usually very poor in contrast to what RME delivers.
And RME's products reach those values...
If RME does not answer to such implementation details like USB transport and its error correction,
then I think they have either no time or no interest (maybe too close to their intellectual property).
This is IMHO fully understandable and maybe you should simply respect this.
If you need information about how USB works, then I would get in contact with open source developers
or look at Linux source code, i.e. of the kernel and ALSA project.
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