Must both transistors in a class AB amplifier push-pull pair need to be matched?
As the emitters are connected together they are working as emitter followers, with voltage gain = 1 (approximately). 

If they are mismatched, you may see a slight increase in even order harmonic distortion, if the open-loop gain and feedback fraction are fairly low.

Some amplifiers may be a bit fussy about matching output transistors to ensure the designed value of quiescent current (and thus optimal crossover distortion), others may require a trimmer pot adjustment to achieve the right quiescent current. Without a circuit it's impossible to say more, so refer to the schematic and service manual for your amplifier.