The term current mirror does not mean the two devices MUST be the same, it means that what happens in one mirrors over to the other. In reality, we often used emitter sizes scaled up to ratio a higher current in the transistor leg. That way you don't have to waste a lot of current in the diode leg to get the current you want in the transistor side. If the transistors are identical, it's a 1:1 mirror. If not, it's a different ratio. We would normally put that info on the schematics whatever it was like 4:1 or whatever in the bias chains.
That is shown above in the schematic where the diode side is labeled "x1" and the other side is labeled "xN", showing that the right side can be a multiple of the left.