I swear this worked a week or so ago, but I haven’t used it since then. (I was playing with it a lot, because of the issue I reported at the time, where the number you enter for scaling doesn’t “take” unless you explicitly hit enter, rather than just letting the pop-out time out.)
Today, when I enter a scale factor for ‘Z’, that scale factor gets applied to all three of X, Y, and Z. I’ve found no workaround yet.