The safety issue at hand deals with the rudder and "momentum" (for lack of the correct terminology)
The problem was repeated full deflections of the rudder and the amount of force that generated on the tail at speeds below the design limit....and post crash in NY, Boeing published an article indicating that their large planes had the same issue. Full deflection left, getting the tail moving followed with a rapid switch to full deflection right, then full left again wasn't a great idea and was something the designers\test pilots never really evaluated since there's no real aerodynamic reason for doing so.
Instead it should be full left-neutral for a bit, then maybe a touch of right\left....etc