No. They could've just said something like "get a new abstract painting in one click" and used phrases like "never before seen". But as-is, their claim is just not true.

What's the difference? For the sake of argument, what if they had an infinite number of images pre-rendered?

Still no, since you’re not _generating_ the image at the point of clicking.

That matters for two reasons, first because words and semantics are important, clear and correct communication is important. Second, the technology required to generate new paintings (cheaply and quickly) on demand is different from the technology required to generate a very large (infinite) number of paintings up front. They’re both interesting but for different reasons, and one shouldn’t be misrepresented as the other.