I kayaked it yesterday probably a couple hours before they put on. And honestly, a high school/college swim team member with a tube and a lot of tubing experience would have very little trouble with middle narrows at those flows. I'm not really upset that the ranger pulled them out, but honestly, to tube that part would involve: lean into any rocks, stay in the current, hop back on the tube asap when you fall off, and have limber knees and ankles to prevent foot entrapment.
Again, I'm not saying it is the smartest idea, but its certainly not a "OMG THEY ARE GOING TO DIE!!! PULL THEM OUT RIGHT NOW AND ARREST THEM!!!" moment.
American Whitewater river info you can use.