The B777 flight control PCUs, especially the ailerons (both inbd & outbd) have like 3 different modes that they operate in. Depending on the flight phase, the PCUs act differently. For instance on TO roll deflect full down, and then an a certain speed return to the faired position.
The deflection u see during approach is normal roll control.
The deflection u see during to roll are a function of the different logics depedngin on airpspeed and eng thrust. The deflection u see during landing roll is a function of airspeed. It has nothing to do w/thrust reversers.
Rather than write about it twice...go here: