alt Hacker NewsSystem completeness can be defined from the product definition. The latter is where requirements and definitions of done come from. Working features are the most important thing and most principles and techniques were about reducing the cost to get there.
If you only accept PRs that implement working features, i.e. you're not gaming it, then it's the same thing.
If you try to come up with an objective definition of working feature you're back to gamability criticism.