I have no doubt that the national media hypes things for ratings. However, in defense of the storm clasifications, I believe they have an arbitrary list of criteria for each designation. I have no idea who decided on those criteria but I don't believe the NWS is padding the numbers to bump a storm up in severity.
As a resident of tornado alley, I can assure you that a simple thunderstorm can be severe.
ETA: Found it... the NWS defines a Severe Thunderstorm as: A thunderstorm that produces a tornado, has winds of at least 58 mph (50 knots) and/or hail at least ¾" in diameter.