The single 1-star rating doesn't have an accompanying review.
The
ReviewMeta for the Topping L30 looks good, granted there aren't many reviews yet.
It's hard to know what to think of that review because we don't know what equipment the reviewer was using before. It's possible that the previous device was not flat, the reviewer got used to that signature, and now the reviewer is hearing and not liking the true sound signature of the equipment. The only way to know for sure would be to have the reviewer take a measurement.
Amir's measurement shows that the frequency response of the unit he tested was flat as a pancake: