This is precisely it. Even the example in the dev blog implies the ability for layered defenses:
From the example, after breaching the outer walls with ladders or a siege tower, the defenders should theoretically be able to fall back to that second layer, with archers on the ramparts and two divisions of infantry holding both inner gates. You know, actually making a siege a multi-layered DIFFICULT process for attackers while defenders have to split and mobilize ALL resources to maintain their defensive advantage that doesn't include the handicap of brain-dead bots unable to climb ladders.
Unfortunately, I also believe it is many of the design choices for siege settlements that further hinder the idea of a layered defense. Take for example the Sturgian scenes such as Tyal, their keep ACTS as part of the outer layer wall where attackers assault, leading to situations like this:
I certainly don't comprehend the logic behind these decisions, however, what is clear is that they all work together to make sieges boring considering the number of times instances like that occur. It is repetitive and an eyesore to even experience. I just hope that keep battles will give more tactical elements to sieges, but from the looks of it, it seems like an excuse to simply elongate the hack and slash elements of the game (not necessarily bad, but disappointing).
Edit: I do feel like I might have teased you guys with that rock, so here is the rest of the siege clip.
Although, if I have to say anything specific about what I felt, it was frustration that while the enemy was trying to flee, many of the troops were simply cheering instead of hacking them to pieces. Although no immediate effects were felt with this battle, when keep battles get implemented, imagine a close siege and a dozen extra enemies are able to reach the safety of their keep because your troops cheer right in front of them, letting them go.