No, they expect that if you're interested in "how various image formats look as they load" and the explanation behind them, that this will be an interesting video to you.
Also, I just skimmed through it: it contains many examples throughout, and given that what's being shown is how an image changes over time as it loads, a video is not an inappropriate format I'd say.
The part where the two of you discuss how Firefox and Chrome now load progressive JPGs with blur instead of keeping it pixelated made me wonder: what happens if I set the CSS of an image to upscale it with pixelation? Does it also force progressive JPGs to stay pixelated while loading?
Good question! I don't know off the top of my head, but since the decoder and CSS are seperate, I think you'll still get the blurred version, but then up/downscaled using nearest neighbour.
