Well, in the ridiculously pedantic sense, flaperons are combined flaps and ailerons so they cover the function of inboard ailerons on the 787. The outboard ones are only used at low speed.
You could be right. Actually I have no idea about the aileron's use in turning at high speed - i would have thought they were, just more subtly? That's the limit of my knowledge :P
I do know however that they are used symmetrically as part of Boeing's "cruise flaps system", which dynamically adjusts all of the control surfaces to optimize wing camber for weight, speed, altitude etc at cruise. Not sure if it's standard equipment.
I don't have a 777/787 type rating but nearly all large fly by wire jets have a system that automatically manages aileron movement inboard vs outboard and things like roll spoilers depending on airspeed. The generic concept is part of ATPL training, the airplane specifics are part of the type rating training.
That's also the difference between calling them inboard ailerons (generic theory) and specifically knowing they're flaperons (787 systems knowledge)
I do know however that they are used symmetrically as part of Boeing's "cruise flaps system", which dynamically adjusts all of the control surfaces to optimize wing camber for weight, speed, altitude etc at cruise. Not sure if it's standard equipment.