And applying that last observation about heaps and waterfalls to the statement in the letter to Menoeceus:
"When, therefore, we maintain that pleasure is the end, we do not mean the pleasures of profligates and those that consist in sensuality, as is supposed by some who are either ignorant or disagree with us or do not understand, but freedom from pain in the body and from trouble in the mind."
Given that we know that Epicurus DOES accept the pleasures of profligates and the pleasures of sensuality as pleasures, the better interpretation of what he is saying is incorporate Epicurus's position on the heap/river questions, to the effect that:
We should not identify the concept of pleasure as being limited ONLY to the particular pleasures of profligates or sensuality (such as sex, food, drink, etc) because that is not our definition of pleasure as the goal. The concept of Pleasure, which we take as our definition of the ultimate good, includes NOT ONLY those particular pleasures but ALSO all other pleasures, such as those of the mind, literature, art, calmness, etc. This "Pleasure as the good" does not exist as a Platonic ideal, it exists and is recognized only by our perception of many particular pleasures. The unifying characteristic of any set of particular pleasures is not that they reflect or partake of some ideal Platonic form or Aristotelian essence, but that we feel it to be pleasure, rather than feeling it to be pain.
It has always made sense to mentally insert an "ONLY" so as to read "When, therefore, we maintain that pleasure is the end, we do not mean ONLY the pleasures of profligates and those that consist in sensuality..." given that we know that sensuality and even the things that profligates do are pleasurable. But placing this sentence in the context of the sorites/heap/waterfall/river question gives us a context in which to supply the missing "only." Waterfalls and rivers and heaps are not ONLY individual grains of sand or drops of water, they are a composite of the individual particles. Pleasure is not ONLY sensuality, but it is also all feelings of all experiences in life which are not painful, because that is a necessary deduction from there being only two feelings, pleasure or pain, into one of which category all feelings must be placed.
You can't recognize heaps or waterfalls or rivers without recognizing their components, and you can't recognize Pleasure as the good without recognizing all the individual pleasures of which the concept of Pleasure is composed.