Currently the firmware in the controller of the RC Pro is fixed to the M3.
In order to support other aircraft it requires a way to switch the RC firmware to allow connection to these aircraft.
The RC-1N loads different firmware based on the aircraft selected in the Fly App. The RCP does not have this ability as yet and is fixed to the M3.
There should be no reason why, in time & if DJI wants to, that the RCP will be able to switch out its firmware.
There are reports of the Mavic Air 2S shipping with an RCP instead of a smart controller. Again the RCP has firmware to enable connection to the Air 2S but lacks the ability to switch to other aircraft.