This is almost exclusively what I've encountered in most of the "elite" engineers. It's frustrating because they're the ones saying coding and job hopping is easy. They're the ones in tech interviews who downplay your achievements.
In my experience, rather than leaving for another company though, they're often a C-suite favorite and get to start some new project (often it's whatever they want to do as long as it's remotely justifiable). They get it up to 80% complete so they can hand it off to another team to do the last 20%.
Since the project is whatever they want to do, they use very unusual languages or design choices that the new team has to pick up and fix. A lot of times it's whatever the big new thing is. (For example, expect statements like this: "Everything is obsolete legacy code now that Electron exists!" "No need to keep this standalone offline test database, setup shell scripts, or maintain the environment setup guide because Docker will automatically solve all of these cases!")
They continue getting new projects because these 1 or 2 people "did the project 80% complete in 1 month, and the last 20% is taking the handoff team of five at least 3 months to do."
Bonus points when it is expanded from some sort of hackathon, or some fake story about how some person completed the 80% portion over the weekend. In the former, all the connections and APIs are hard-coded and faked for their demo. In the latter, they had actually been working on this for the past couple months instead of doing their assigned work which made their official team look even less productive.
I was on the teams always picking up the last 20%, but I got moved onto the 80% team once. I was amazed at how much code I could blow through with time to spare when I didn't have to worry about all the edge cases and minute details.
Unfortunately, I got temporarily moved onto a company-wide prod support team which then got cut due to covid. Hooray.