It only matters if the capacitor is acting as a filter in the audio band, like crossover filter, or feedback phase compensation.
If it's part of high freq noise filter, or a coupling capacitor or part of power supply then larger value will work fine. I would go with the value in the schematic.
More likely explanation is they ran out of 4.7s or problem with them, so engineer substituted 2.2s for temporary. Who knows why.
It wont hurt to try 4.7. If it sounds weird go back to 2.2. They are very cheap. Nichicon low leakage sounds excellent. Make sure new parts will physically fit before ordering, and that the temperature rating and voltage rating of new caps are equal or higher value than the old parts.