Yes, indeed .. but there is not much fat in the OEI continued takeoff sums FOR a Vef failure.
Fat considerations -
(a) the failure probably will be not precisely at the critical speed
(b) ops are not always TOD1/TOR1 limited
(c) apart from close in first/second segment obstacles, the net/gross margin gives an increasing pad as the takeoff progresses.
The certification process takes some steps to account for average pilots and startle considerations ...