Quoted from Baiter:

In the PS4 industry the story line, game rules, art, etc are not even performed by programmers. In the pinball world the programmers take on both rules development and coding of said rules. For example, I've suggested that Stern use Lyman to help flesh out rules on all games rather than have him only involved in every third game, but the pinball industry even beyond Stern still tends to use one person on both roles, and as a result games are hit and miss. To be clear I'm not asking that Lyman write the rules for all Stern games, but he is better than most at fleshing out details that can make or break a game.