Why are some apps automatically pre-selected in Allowlist?

Once you choose Allowlist blocking, all system apps are gonna be automatically allowed and you cannot unpick these. Other system apps in the package that is present in your device from the beginning (such as calendar, calculator, contacts etc) are also pre-selected, however, you can unpick these anytime.

AppBlock app is a special case. Our app is always allowed and you cannot deselect it. All the other apps that were installed into your device manually are not preselected and you can manually allow these.