DraftingMan,
You pointed out a sort of inconsistency between wording of para. 1.4(k) and para. 2.1.1.4. Please notice that 1.4(k) does not say about "implied basic ANGULAR zero dimension", but "implied zero basic dimension", which may actually include both, angular and linear 0 basic dimensions, even though the paragraph refers to para. 2.1.1.4, where only basic angular dimensions are discussed. (FYI, it has been slightly improved in the draft of the future version of Y14.5).
If that does not convince you, I would like to ask you (or someone else) following question:
If zero basic linear dimension is not implied per 1.4(k), then why is this dimension not shown in fig. 7-56 in Y14.5-2009 (and in many other figures in the standard)?
CH,
I am looking at fig. 4-33 in Y14.5-2009, and I would say the if on your sketch design intent is to have both slots disposed symmetrically on both sides of the datum center plane A, you do not need the red dimension. With that being said, in order to avoid confusion I would use two basic half dimensions instead of one.