I am not talking about the construction of the mobo assembly.
I am referring to the final computer assembly when the power switch, HDD LED, and headphone/microphone jacks mounted to the chassis are connected to the mobo.
The mobo is QA'd before the final assembly team gets it on the production line. If a computer is assembled on site such as BestBuy etc, there probably for errors is very high. If someone assembles the computer at home from discrete parts, there is a good chance as well something may be missed.