The Necromancer's Path.

Otherwise... more often than not, in my experience, Benedict besieged the city upon first encounter, but the AI's ways are mysterious.

I have a save file from this situation. We launch it and immediately end the turn (Naadira doesn't move). Benedict attacks Naadira, then captures the lumber mill, and after that, uses the portal to enter the city. I'm posting it so you can investigate why Benedict is playing this way here.