The purpose of these would be to provide an inexpensive, better headphone output to drive the DI with. Nothing more, nothing less. I make no claims as to the quality of the headphone output of these USB adaptors.
A while ago I bought a similar (though not the same) small USB "soundcard" thinking it could not possibly be worse than my laptosp 3,5mm output.
Was I in for a surprise! The thing manages to be worse than any laptop soundcard I've ever encountered in lots of different ways!
Fortunately the thing was very cheap so it was not an expensive lesson. A lesson learned none the less ;-)
I now plug my laptop into an Allen & Heath Zed 10FX as my USB interface. Much better
On some very small jobs I might not even need any other mixer, for anything else it can also be a little submixer.
S.R.