Well, Billy, that's a very good question. Some folks may consider Bonneville 'severe duty' but if you look in the owners manual I believe the defintion of severe duty is more along the lines of lots of idling, trailer towing, stop and go driving, hot or cold temperature environments, etc.
Since a few quick blasts down a one mile course at Bonneville doesn't fall into those categories it isn't considered severe duty, IMO. But hey, that's just me. GM will have the final say and I just have to sit back and wait to see what that is.