Antifragility describes a system that becomes more resilient automatically, because it is built such that it must, in response to attack or damage. Such a system doesn't require management. It doesn't require people to actively test, to think about how to make the system better, to implement the fixes.
I think that's an overly narrow definition of the term antifragility and interpretation of the system in this case.
While I can imagine software that is in itself antifragile, I think it's entirely reasonable to include the totality of the people and process that make up an operational system, in which case even your narrow definition applies here.
If you are including the developers in the system you're calling antifragile, then Chaos Monkey is also part of the system. Antifragility refers to a system that benefits from attacks or disorder from outside itself.
You are watering down the word so much that it wouldn't have reason to exist. Is every chair-making process antifragile since chairs get stress tested before being sold?
Chaos Monkey is just a tool to accelerate/simulate the disorder inherent to the cloud. The original point was that the cloud is unstable and hostile, so software designed for it benefits from that disorder. Granted, it's not doing so all on its own, but exhibits the effect nonetheless, and I think Taleb's book is full of similarly impure examples.
There's a world of difference between stress testing before something is sold or released and welcoming ongoing hostility throughout its lifecycle, and this difference is absolutely in line with the concept of antifragility.
