If you look at the washing yeast thread. When you first put the water into your carboy of trub, the very bottom layers are proteins and hops.
My understanding is that you generally want to keep your wort away from those bottom layers. Washing keeps the trub from imparting any flavors into your beer.
I haven't heard any problems with the flocculated yeast. As far as I understand, they'll wake up and start eating again, but the main issue is with the non-yeast particles at the bottom of your cake.