Other people have made the same observation about the signs of the dysfunctional process table. When I wrote it, I was including stakeholders and managers as part of "team". So the scenario you describe would be the business side of the team not managing the scope properly. I'll need to update the table to be clearer.
I agree that people don't change quickly. In those cases, you need to adapt the process to guardrail them (e.g., add a check in the workflow) or put a different person in that role. If you don't, you're just going to get the same result again in the future.
For your edit -- is that a bad thing? Presumably a architect should be able to explain their decisions. The major theme of the guide is that communication is a good thing, especially when the different people are likely working with different information and expertise.