It sucks to do a 2-line change that requires 2 weeks of validation :/
Agree that codegen can flip the effort from creating to validating. Some people believe the "true" intellectual capital created by the software development process is the understanding created inside the team's mind as they build it (not the code itself). Like, understanding of the domain, customers, market, how the software works, how they would build it again if they had the chance, their networks and relationships etc.
Probably it does hurt if codegen impacts that process. It's always been possible to externalise some of that understanding, by writing books, articles etc. I suppose what we are starting to see is that kind of intellectual capital will gradually reside in AI also. For well understood problems (TODO app, space invaders, etc) the model will have the actual understanding and everyone generating those apps for the first time would need to build it up.
I agree that 1 LOC that provides infinite value sounds like the "best possible program", but beyond that I can't see any hard and fast rules about LOC vs value, I think they're almost entirely uncorrelated. Mostly it's about what the lines do, but even then it's hard. What's more valuable: the bible, the script to star wars or a set of 747 technical manuals? Should they have used more or fewer words to achieve their goals?
Even with precise specifications the "best" way to implement large scale software is never clear and depends on many factors. Sometimes more duplication is better, sometimes you need more abstraction to reduce it. A lot depends on what your team (or contributors) are comfortable with and their abstraction ceiling.