Script as Updater is needed if a script file has to modify a solidified system. It requires patching of the ntdll.dll that is loaded in an Interpreter process. The patching is needed to make sure that MACC is notified when a script is being run and a check the updater rule is configured for it. The patching of ntdll.dll makes it vulnerable to issues. As of now, a Script as Updater bypass does not exist.
Script as Updater is to be injected only into script interpreters' processes, not all processes. When applying an Application Control key while MP is disabled, scinject.dll is injected only in script interpreters. The same logic exists for the Execution Control feature, which needs to hook the same functions as Script as Updater is hooking.