Besides the difference in velocity, consider the general arc of each pitch. Anderson’s changeup veers downward gradually, whereas Giolito’s changeup fades suddenly, ending up at the bottom of the zone. The numbers corroborate this observation, too: After adjusting for pitch height, Anderson averaged a -6.8 degree approach angle on his changeup; Giolito averaged a -8.0 degree approach angle. The relative “flatness” of the former changeup is reflected in what we observed in the above GIFs. And no, this isn’t because one pitch generated more vertical movement than the other – according to Pitch Info’s measurements, the difference between the two is practically a rounding error (1.32 vs. 1.38 pfx_z). Identical destinations, alternate paths.
What does this all add up to? My hunch is that due to its shallower entry into the strike zone, the changeup Anderson throws resembles his four-seamer quite strikingly until, wait, it doesn’t! Cue the awkward swing and miss. This makes up for the absence of a large velocity differential – in fact, the zip of the changeup might be what keeps it line with the fastball, in conjunction with a high spin rate. There’s not much separation as a result, but maybe that’s the point.
I see the point about the change playing off his fastball because of the lesser delta between fastball and change, but is he also saying that there is such a thing as "late breaking" stuff? Recently a lot of analysis suggests that's an illusion, but my personal experience and observation (which I've been questioning in a lot of my baseball knowledge over the last decade) has suggested there's something to it. I think about the interplay between the ball and the air and think, given the seams and spin rates and speed and the resistance of air, there might be the possibility that two pitches that break the same total amount would have two different paths. Especially when I think about Greg Maddux saying he wanted every single pitch to have a short, crisp, late break.