An instructor of mine many moons ago completed the robinson safety course and while up flying with one of those test pilots they chopped the throttle at 102kts and didnt dump the pole for 5/6 seconds
just did a very harsh flare , then dropped the collective.
as for 1.5 seconds , frank says 1.1 seconds but that all depends on power aplied, density alt etc.
Bigger helis , heavier blades and more time to react , however if you lose the rrpm in the robbie it is easy to get it back , in the bigger helis it is harder to lose the rrpm and likewise harder to get the rrpm back to the desired . Am i making any sense?