Either can be correct based on strategy. Flat paint is great as it is a slightly less expensive option and does hide some imperfections. The more sheen a paint gets, the more obvious it shows damage/repairs, and the harder it is to touch up without obvious flashing. The flip side of this conversation is the more sheen the paint gets, the more durable (impervious to stains) it gets and will last longer.
In short, if you can hold vendors to a higher standard when making repairs, go with eggshell or satin finish. If you want a little more "play" in repairs and greater ability to touch up, go with flat.
We go with full gloss everywhere for durability and longevity.