Will,
I think the interim recommendation addressed two areas of concern. The power increases not only add heat to the FOHE but also cause the fuel flow to increase dramatically above idle rates, forcing accretions to break up and move on down the pipe.
My comment earlier was referencing the Trent's new FOHEs, so I may have mis-quoted your meaning. Apologies.
I agree that there is something odd about what has happened here and once again am left wondering out loud how this could have been missed by Boeing, Rolls and the regulatory bodies during certification. I think something changed and it smells like kerosene to me.