by numbers
Any discussion about Jacobsen's technique gets mired down in the number and seems to miss the main point that arises; that it gives a very accurate method of using the visual cues that are readily observable in front of the pilot, when conducting the flare commencement and rate determination. The off nominal condition for path and speed/attitude are in the first instance easy to compensate for, and in the latter case self cancelling in effects. The technique remains just that, a technique, not a policy, procedure or mandatory practice.
I have taught and demonstrated the technique on occasion where the student showed an interest in the concept, and have used it in a variety of different types from light aircraft, western and soviet era military jets, B747, B744, B767, B777, A330, and MD11.
It is a very accurate additional cue available when understood, that may be used by the pilot to assist in his perception.