If we are using “twice as productive” to mean that a typical developer can complete twice as much work (not just writing code, but overall work) in a fixed amou

If we are using “twice as productive” to mean that a typical developer can complete twice as much work (not just writing code, but overall work) in a fixed amount of time, I’d put that at ~5%. If we are talking about specific workflows, I would agree with you that this is quite likely to occur.