It does not do what it claims, it is not a step-down converter, the only thing I see at the output is a small voltage drop due to losses, something typical and not an indication of a problem, but this does not change the fact that it does NOT do what it says.
The test was conducted within the voltage and current limits mentioned in its specifications (with a load of about 14 mA, many times below the 3A maximum limit it claims to have), the variable resistance that is supposed to adjust the voltage also does absolutely nothing (unless it is for current, but even then, besides the fact that I did not see any change when I tested it, for a voltage step-down converter and not a current regulator, it does not make logical sense for it to exist for any other reason than voltage adjustment and how little you can adjust it, clearly it cannot take, for example, an input of 2-10v and give you the minimum mentioned, 0.8v).

Furthermore, the even more ridiculous part of the situation is that one of the two, as you can see in the photo, came with a literally uprooted output smoothing capacitor (clearly visible in the picture). I cannot give it more than 1 star, I would give it 0 if possible because it is simply, literally, useless and misleading. Anything I have bought from Aliexpress (around 20 step-up and step-down converters) I have never had any issues, it's ridiculous.