This is the right amount of brevity, IMO. "Omit words" doesn't give you a hueristic about what to omit. "Needless" gives a test you can apply to every word. "O

This is the right amount of brevity, IMO. "Omit words" doesn't give you a hueristic about what to omit. "Needless" gives a test you can apply to every word. "Omit words" sounds simpler, even obvious, but only because you know it's a shortened form of "omit needless words". We could shorten the advice to "simplify", but that doesn't give you the how.