The both techniques for ploughing in a robbie have their good points and not so great ones.
The 60kts at 100ft and then flare to come to the hover is an old technique, that I know of used in the Uk for a while, Keeps you out of the avoid curve, but when training the students and the subsequent solo's, it was found alot more incidents with stinger strikes, very close calls and instructor heart failure.
The now maintaining a constant rate of closure, constant angle of approach.
Allowing the speed to slowly wash off when starting an approach, the student has an improved judgement to not to stack it when coming through 100ft, yet you do get some interesting students that will not understand the concepts and allow the speed to decrease to a certain point on the approach to an unsafe level.
None is right, none is wrong. Its your judgement of the students ability for him to judge closure rate and then make a decision.
fluffy