Impedance matching in common collector
Think about it this way. 

If you had a 12 volt light bulb that has a resistance of 12 ohms and you applied it to a 12 volt power supply, it would produce a certain amount of brightness based on the power consumed.

Then, you insert a 12 ohms resistor in series with the bulb and looked at the bulb’s brightness.

In which scenario is the bulb the brightest?

In your question you are putting the cart before the horse and assuming maximum power is obtained when the source impedance matches the load impedance. In fact it’s when the load impedance matches the source impedance that you have the maximum power scenario.