I've seen the opinion in your second paragraph expressed in various places, BBM - sheer nonsense, in my view.
The first examples of subtractive anagrams that I came across were jolan's, and he never thought it necessary that the letters be in order.
(It's similar in concept to a very irritating book I read recently - "The Luminaries" by Eleanor Catton. It has several sections each of which has precisely half the number of letters (or was it words?) of the previous one. My response was "Why?")