I don't think it works that way. During the course of your professional career as a developer you change jobs. And let's say that at every job you create APIs.

I don't think it works that way. During the course of your professional career as a developer you change jobs. And let's say that at every job you create APIs. Besides the particular functions those API provide, the API code itself (how you interact with clients, databases etc.) will be pretty much the same as whatever you did at previous jobs. Does this constitute copyright experience or is just experience? My analogy is that if Copilot doesn't provide 100% code from another repository it is OK to be used by other people trained with code available on GitHub.