Valandar means that in frame 1, parented prop scale is 100% and unparented prop scale is 0%, and the same goes for frame N-1. No interpolation - constant section in graph. At frame N, where you "unparent" the prop, parented prop scale is 0% and unparented prop scale is 100%. What I also do is just move them in and out of frame, like going from y=10 to y=0.7, so one appears suddenly and the other disappears at the same time.