> Or the creep in Starcraft.

Starcraft is an interesting example as it combines both (or three? I'm unsure whether Protoss can build in the radius of enemy protoss energy suppliers) approaches. It also has only very few exceptions to the eternally loyal robots.

In Settlers, you have to imagine that your people are frightened by the enemy soldiers, and then you have your ingame explanation. Clonk has only soldier that are directly controlled by the player, so restricting their ability to raise a flag feels wrong. Sure, make the robots in the buildings keep their allegiance to the flag that was there first. But what is gained by requiring the player to first destroy, then raise instead of letting them choose the order? That way, the defending player can sometimes also have the choice between destroying the attackers flag and defending their own.