We may not be talking about the same thing, here.Depends on the degrees of the stem. 7deg you are very close, 35deg it does change a little.
It is true that if all you flip a stem from down to up that the reach to the saddle is reduced. Further, as you correctly state, the 35 deg stem will do so more than the 7 deg stem.
However, the point I was making (in response to DrSmile's post) is that raising the bars the same amount via spacers leaves the bar in an identical position, with identical fit and handling characteristics. In other words, using spacers to raise the bars also decreases horizontal reach to the saddle, just like flipping the stem.
DrSmile was suggesting (if I am reading his post correctly) that it is better to use spacers rather than flipping the stem, because flipping the stem effectively shortens it. While it is true that flipping the stem shortens it (sort of, depends how you are measuring it, and for what purpose) using spacers does the exact same thing.