And why would the other agent react any differently to the delegate than to the source-code change or the decision in the moment?

Let's go a bit more meta...

The world is imperfect. And we all know it. Therefore, when faced with an imperfection that seems inevitable, we often forgive it.

But people don't have correct models of the world, so they can't distinguish reliably between evitable and inevitable imperfections. This can be exploited by creating imperfections which seem inevitable, and which "coincidentally" increase your negotiating power.

For example if you hire agents to represent you, your customers usually can't tell the difference between the instructions you had to give them (e.g. because of the imperfections of the agents, or possible conflicts between you and the agents), and the instructions you have them deliberately to make life more difficult for your customers. Sometimes your customers even don't know whether you really had to hire the agents, or you just chose to do so because it gave you a leverage.

The answer is in some form: Customers don't have full knowledge about what really happened, which includes knowledge about how much their lack of knowledge was used against them.