All the CB550 engines were effectively the same, both F model and K model. Neither model offered any performance advantage over the other, except maybe in overall weight.
The gearing was the same as well. 17T front and 37T rear sprockets.
The Wiki article is just plain wrong.
Maybe the writer got confused with the CB500?
Anyway all the engines were red-lined at 9200, but would go over that line easily. Just how much, I'm not sure? I wouldn't be THAT surprised at 11000, with a good valve spring set, and a very good points set.