Thanks for the reply. I guess this was just too obvious for me to realize - I would have guessed it would have had something to do with the reliability or consistency of rotational strength.Tornadoes are rated by the damage they cause, not by their rotational signatures. If the strongest tornado ever recorded were to sit over an empty plot of dirt and not hit anything, it'd be rated EF0-EF1, regardless of how strong it actually was. In order for a tornado to be rated EF5, it has to 1) Hit a structure well-built enough to require EF5 level winds to sweep it off the foundation and 2) Actually be producing EF5 level winds at the time the tornado crossed over the structure, as EF5 level winds only occur for a very brief period of time and over a very small area in the majority of tornadoes that earn the rating. The only instance I can think of in which a tornado was rated EF5 due to damage not inflicted on structures was the Philadelphia tornado from 4/27/11, due to the fact that it dug a 2 feet deep trench through a field.
I know this dead horse has been beaten to a pulp already, but it does seem very odd that the experts who rate tornadoes would ignore objective indicators of strength in favour of subjective indicators of strength.
I've also heard it said that Greensburg (2007/05/04), Bridge Creek (1999/05/03) and Andover (1991/04/26) were probably not the most violent tornadoes of the outbreaks that spawned them in terms of absolute strength, just the most damaging. I'll try to get a link to the source (I think it was from ustornadoes.com).