Are you sure? Modern radios have 8.33 kHz spacing.
Yep - sure enough. Certainly there are many modern radios that allow 8.33kHz, and it might be there is an update to the aircraft RMP as an option, but both the Bendix transceiver and the RMP state the tuning step as being 25kHz for the basic Airbus offering.
I'd be interested to hear from any current A320 crew who find this is incorrect and 8.33kHz is available.
- GY