Compression with extra steps is still compression. Most people don't understand the math involved in LZF-encoding, and lossy audio encoding seems even more strange, so "diffusion" just sounds like a somewhat-lossier form of compression if described in a certain way.

I was very dismissive of the anti-AI-image crowd until I saw that Anne Graham Lotz pic. Only a single known source image of her exists, although many copies of it are distributed far and wide across the internet, and using her name in a prompt results in an image that seems very much like a lossy reproduction of the "original." It's an edge case, to be sure, but that demonstration looks like lossy compression, even though it's not.