I disagree, I find "omit all words" to make as little sense as "omit no words". Personally, I find it more likely to default to "omit some words". This, of course, does not describe the type of words we should be omitting, but rather that there exist words that we should omit. Saying "omit needless words" does describe the type, adding more information which is not there otherwise, making it a "needed" word.