Not sure whats modeled for IL2 1946 I would imagine its simplified and could be that its a Kommadogeraet/Bediengerät
The Jumo213A is not managed by the ATA setting.
the "Bediengerät" manages the engine settings, dependent on RPM, regardless of ATA , dependent on altitude airspeed etc.
Here's a Kommadogeraet overview image.
As for the diving problem ..................... you would have thought it was safe to reach those speeds.