@Stefan – this behavior has changed from CC v9.2 to v10.0.
To get what you want you need a ExtendScript (JavaScript) once written by John Hawkinson. That code snippet will change preference settings not exposed to the user, the Custom Monitor Ppi, to 72 ppi and enable their usage.
app.generalPreferences.customMonitorPpi = 72; app.generalPreferences.useCustomMonitorResolution = true;
Before running the script, it would be best to check, how the actual values are with the following snippet:
alert( "Custom Monitor PPI currently is set to: " +app.generalPreferences.customMonitorPpi +"\t\t" +"Usage is set to: " +app.generalPreferences.useCustomMonitorResolution );
To change this behavior back to default, use the following line of code:
app.generalPreferences.useCustomMonitorResolution = false;
Uwe