Right, buying the amp, opening it up, knowing the topology, measuring it and listening to it is not enough, one should go to Topping factory and interview the actual person who assemble that particular amp.
Be open-minded, the dirty solder, the square wave output and even the disconnected connector might have profound reasons we do not know of.😀
Those could be the "secret sauce" of Topping's world-class measurement performance, Topping engineers are top of the world, they must know what they are doing.