Comment by Madmallard

You can make skills files all you want and have testing agents that evidently reduce need for revisions post deployment but it's not 100% and the more you don't understand what's going on because you didn't write it, the more complex the system is, especially if it's not all testable in a way that reduces risk, and especially in a security-relevant system or one that could have consequences to people the worse all of that is.