I agree, the x-axis labels are not helpful! Thankfully, the first example is “buttons with corrected icon spacing”, and the image on the right looks much better than the one on the left (a bigger difference in quality than in the other two examples), which is visible when the slider is on the left.

Suggestion to devs: put the label “material-style” in the lower left of its image and “liftkit” in the lower right of its image, and cover them appropriately as the slider moves, and then it'll be clear which framework the current image (or portion of it) belongs to.