I think you're saying what I mean, but I'm not quite sure, so here's how I came at it:

Evolution relies on mutation, and mutation is random. If a certain feature is currently observed, that doesn't mean the mutation has already occurred and been selected against; it might just not have occurred, or not widely enough to catch on. For example--just because skinks lay eggs doesn't mean live birth isn't a good mutation for some of them.

In general, I don't know that it's ever accurate to talk about evolution in the past tense when referring to a living species.