"Good artists copy, great artists steal" doesn't seem to me to about how wholesale the copying is but that the copy exceeds the original in creativity, beauty, or some other quality so much that it displaces the original, and makes the original seem like the inferior copy.

In that case copying something that is merely mediocre in most respects but has one outstanding quality, and generally exceeding it, makes sense.

I'm not sure any of that applies here except maybe that Anthropic might be more poised to make anything they publish suddenly very famous.