However, that still does not negate the passing or asking of the seating distribution when passenger breakdown figures are passed from passenger services to load control when you have a non-integrated EDP system in play - that remains (in my opinion) the fundamental process breakdown and the primary cause of this error and eventual problem.
As for,
"Load Control then had to manually re-distribute pax to get W/B within limits, just forgot to tell gate & crew about it."
If this (as you posit) is correct it suggests that a seating distribution was passed and entered in the load control software solution which then presented the out of trim circumstances to load control, if true, then as such the first thing one would do as a load controller is tell passenger services of that issue immediately and the need to reseat or whatever other corrective action was required. Failure to do so would be criminal - for want of a better word. To actually go on to prepare and present a load sheet under those circumstances knowing full well the action you took to produce it and to not tell anyone else ... well.