[SwissXC90]

That all sounds right

A sub can be loaded or removed as it was foreseen as an optional component that could be fitted any time.

The main car stereo was configured at the factory and Volvo never foresaw that a car would be up- or down-graded from one level of stereo equipment to another level. So while you can fit the higher-level components from another car, your car, and any VIDA connected to it, still expects the old system to be fitted.

Whilst the actual config that changes what is in the car is quite simple, and Russian hackers have managed to hack the CEM and change the config, the Volvo dealer has no access to any tools to change the CEM config in a way that was not intended.

(The CEM config is also protected by a PIN, which takes over 24 hours to crack using a brute force attack).

So your experience is all in line with expectations.