The 2 seconds acceleration after V1 certification was amended in the early 90s to be replaced with a distance equal to 2 seconds of travel at V1 speed. Not the same.
Indeed. However one needs to keep in mind that the acceleration was with the remaining operating engines, and the distance at the V1 speed. So the rundown characteristics need to be taken into consideration when considering "not the same". As the rationale was to inject a pad for those things which catch us out, the distance requirement is more readily comprehended.
Yes, you've still calculated the perf with the 1.15 or 1.3 margin for good reason.
I'm probably just having a slow day .. the factors relate to ?