it seems easy to you?  There is a wide range of skills out there and rapid rating apply not only to people in properly outfitted creek boats, but in every other type of river craft (including those "dreaded" cherrycreek type rafters and tubers) out there.

I have not run stateline falls but have seen a bunch of pictures and video.  Taken by itself on the right day with the right water level, it doesn't look terribly difficult as long as you are on a fairly precise line.  The f-up potential seems fairly high though.

Instead of downgrading the rapids, go with the AW standard ratings, recognize that maybe you are a better boater thann you think, and also recognize that there are a potentially infinite number of 5.x levels, each one representing a full class step up from the previous level.