It's not hard to test. Go to a page that demands PoW, change your IP and see what happens. I just did it. Spoiler: kernel.org asks for a new PoW.

If the source IP was an issue, you could do it other ways: for example, make the cookie rotate on every access, and insist there is a single stream of accesses.

Why are you and other defenders of the Anubis approach so fixated on this one specific limitation of a certain type of scraping architecture? It’s hardly an immutable characteristic.

You say “they” as if all scrapers are a monolithic group with the same constraints and goals. Part of the problem is the massive diversity.