Been doing this software thing for a bit now… while what you say is true in that it is possible in some rare cases, I think it’s a bit of a straw man exception. Code is, in the general sense, unfortunately never complete, regardless of how complete it seems in its context.
The issue is that the context is always changing. It is almost like suggesting there is an evolutionarily perfect organism. At best, one suited perfectly well to the current context can exist, but that perfect suitability falls off the second the environment changes. And the environment always changes.
I totally get the sentiment, but I think the idea that any code is ever complete is unfortunately just not a realistic one to apply outside of select and narrow contexts.