I thought about it for a little bit and came to the conclusion that is a good idea to trim the fan leaves during the flush. There is stored mobile nutrients in the fan leaves. Leaving them on would result in the newer growth and leaves close to the flowers to live off these nutrients leaving them with a bad taste. If you cut them off The new growth would not have those nutrients to live off of, It would then start living only off the clean water, leaving the buds with a proper flush. This is a much faster and efficient flush than leaving the leaves on.
Really smart idea you thought up. I will start doing it as well.