At the AAA game studios I have been an engineer at, the core/systems/lead designers have all been very familiar with game history, are avid gamers across genres, and always have, for any idea, examples of how that idea has been done in other games or that it has been promised in upcoming game X, etc.. The junior designers I've worked with have lacked that skill, which is probably why they are mostly just a cog in the content pipeline. Much as there's a difference between a real engineer who can build up systems and an enterprise UI programmer, there's a difference between content "designers" and systems designers.

Hands down, though, the best systems designers I've worked with have had programming backgrounds.