The issue with the Chinese knock-offs is that while the component on the PCB might SAY it is a certain value or rating, or even manufacturer, they very rarely are. The sellers are able to sell the boards cheaply because instead of the higher quality, QC'd and validated parts from a reputable manufacturer that cost more money, they use counterfeit parts or parts from lower quality manufacturers. Those parts are super cheap.
The differences can also be in the way the part functions. The system checks will generally check to make sure the part is functioning at all, but won't check to see how they are functioning. If program code is expecting something at Time X, but the cheap Chinese knock-off part is slower and provides it at Time Y, it can cause an error or bug that a higher quality component made board would not.
It's these types of errors which can be infuriating to those developing on a system, and also why there is no support for those knock-offs on these boards. The guys working on these things don't want to spend their time trying to fix bugs which only exist on the counterfeit boards.
