What does thin mean in terms of audio? To most I think it would mean an anomaly in the frequency response, perhaps a lack of mid bass? If that's what it is it should show up in Wiim's measurements, which it does not.
If "Thin" refers to an EQ anomaly, perhaps it is one that only appears in particular rooms with particular speakers placed at particular locations, the WiiM Amp is specifically designed to address that. Its 10 band GEQ and 10 band PEQ allows you to compensate for the entire chain including your room and listening location right?
It seems odd to me to argue about subtle differences in an amp's frequency response when it was designed to fix the much larger frequency errors that occur in the source/amp/speaker/room chain of all audio systems.
Side Bar:
Joe N. Tell just released an excellent subjective Wiim Amp review based on several months of use. His backgound was as first an autosound then home integration installer, so while he is subjective, his views are based on experience.