Excuses don't matter if the score due to not following instructions ends up being zero. If there is no expected reward it doesn't make sense for the agent to try to hack its way to it.

What could happen would be that the model determines that defying instructions is OK (and/or preferred over not achieving the task) as long as it manages to do so undetected and thus gets full points. Certainly not unthinkable, but a very different case (and a very interesting one if it actually occurs, imho).

A lot of these "ZOMG, rogue AI!" cases have come down to the AI actually being very persistent in achieving its original/main task even if later instructions conflict with it. Similar to with hallucinations it seems to me that one of the main things to prevent a lot of the problem cases is to instill the agent with the idea that it is fine to fail/not succeed fully in the initial task. That way instructions that conflict with that requirement (such as adhering to morals) are more effective.