I agree that there's value in unfinished projects. I think Jay's talking about those who are constantly re-vamping their "process" to match the next thought leader on the Internet, those who are ...
https://jayvie.com/blog/2011/06/04/dreamers-and-doers/#comment-17
I agree with girard31 - I hardly ever walk away from an unfinished, rejected or not-the-right-time-for-this-idea project without having learned something important from the experience.
https://jayvie.com/blog/2011/06/04/dreamers-and-doers/#comment-12
Projects attempted but rejected or unfinished are part of the process. The time spent doing them is not wasted if you learned something in that process.
https://jayvie.com/blog/2011/06/04/dreamers-and-doers/#comment-11