We know that a quadcopter needs to be tuned to its perfect PID values to minimise the pitch, roll , yaw errors and etc., Before releasing to the market will they tune every unit and ship it ? Or a any different algorithm is used which doesn’t require any tuning ? Because every motor/ESC or a chassis will not be exactly same, which will add to the noise.
If you want to build thousands of drones, you will use the same ESC, the same motor, the same chassis on each drone, with an assembly process that will make every drone identical. Therefore, you'll have less than 1% of variation on your mechanical characteristics (momentum, weight, and so on). This is far less than the variation of propellers performances due to temperature, pressure, and hydrometry. There is no reason to worry about that, automation is done to deal with it.
PS: it's also less important than the imperfection you introduce by tuning your drone by hand. The tuning of a PID (or any other regulator) is never perfect.