Can Unity not replace customized values on re-imported packages?

I established in a previous question I asked (and answered) that when a Unity package is re-imported, it replaces the customized values in the inspector in duplicate scripts with the default ones from the new package. This means that if you import a script, set a value, and then reimport the package, the value will have changed. Is there any way to override or change this import behavior? Is the asset post processor somehow tied into this? If so, how does it work, in layman's terms?