thing
What you are talking about with your uncle is the airspeed gap (in those days) between normal unstick speed and the higher speed at which full power on one engine and nothing on the other could be controlled by full rudder and a bit of aileron (this speed was often called single engined safety speed now V min control air - Vmca - with today's certification paperwork).
I believe with some WWII types it could be as long as 30 secs before this extra speed could be built up. The only solution with such types was to immediatley shut the good throttle and glide in straiight ahead. Any delay and it was likely the aircraft would roll uncontrollably into the ground.
Today airliners have a Vmcs that is below unstick speed (you will be pleased to know)