"Less Moved Code Implies Less Refactoring, Less Reuse"
That's a design opinion. At one time OOP people said classes should be closed to modification and open to extension, i.e. that you wrote code and once it worked, you didn't mess with again, unless you screwed up.
Anyhow, projects like Aider (and to a far less extent my sideproject) are working on ways to get bots to read existing code and edit it, which is currently a hard problem.
https://visualstudiomagazine.com/articles/2024/01/25/copilot-research.aspx