Is common in games, what has happened to people I know is they get a job and then build the mechanics of a game, they then get fired while the art is discussed and worked on, then rehired to finish the work as nobody else knows how it fits together anyway.
What's wrong about it? You should just charge more in expectations that the job won't last long and you can work at different company on different game mechanics after getting fired. Employing people you do not need is not efficient for both the company and economy.
