Just adding some info to clear things up. It is correct that that the Digitakt audio inputs are not connected to main over USB when it is used as a Class Compliant divice. The reason for why it is like this is rather simple. These inputs are not connected to Main in the Digitakt device either. They can only be heard when you monitor them as inputs for sampling. This is how it is designed.
But I hear you, it would be nice if they did connect to main as the audio inputs do on Digitone. No idea if this is posssible or not, but I’ll mention it to the dev crew 