Why should rice be cooked uncovered?
You can cook rice covered or uncovered, it will not impact the flavor.  The amount of liquid you begin with, and your cooking time, could certainly be impacted. There are several methods for cooking rice (covered, uncovered, and both).  If you are using pre- or par-cooked rice, the directions are likely just a finishing step, formulated so that you don't over-cook the product.  You could still use a cover, but would likely need to keep a close eye on it or experiment a bit to get a result you like.