> What type of compression would change the relative scale of elements within an image?

Video compression operates on macroblocks and calculates motion vectors of those macroblocks between frames.

When you push it to the limit, the macroblocks can appear like they're swimming around on screen.

Some decoders attempt to smooth out the boundaries between macroblocks and restore sharpness.

The giveaway is that the entire video is extremely low quality. The compression ratio is extreme.