I would actually express a different theory, namely having to do with how your peripheral vision handles contrast and color sensitivity.

Essentially the various planes and geometric shapes of the face become very difficult to read. Mostly the cheek planes extending backwards in space. Notice that all the images are using frontal lighting with a fairly even wash so the contrast on these planes as well as under the brow (etc) is very small.

What this means is that when a new picture appears you suddenly see the entire shape of the head as "face". And so for a brief instant even someone thin like Jennifer Aniston looks really fat because (or at least "misshapen") because the face isn't be read as a 3D form.

Here's an example of what your eyes/brain are doing

In all of these photos the planes of the face (mostly foreheads, cheekbones and chins) are at a low value contrast and our eyes would normally be gathering information because of hue contrast...which they can't do as well at the peripheral.

That's the primary key.

Another key is that having faces displayed in sequence also points out the variations in facial structure which most people don't see or observe. Because we personify people by their likeness we rarely deconstruct it. Most people would be largely unable to say why a face differs from a standard skull/face...which is precisely why most people are largely unable to drawn an accurate portrait.

Displaying faces of different structures in rapid succession will accentuate these differences to the point that they are observable to most.

tl;dr Low contrast peripheral vision leads to an incorrect 3D understanding of the face. Plus faces are weirder than people are able to see.