"artificial selection" means people selectively breeding for traits they find desirable [0] [1]. e.g. "I want a short-legged dog, so I'm going to keep breeding the shortest-legged dog from each generation together." That's not what's happening here. The poachers aren't trying to create tuskless elephants.

You can't peel off the "natural" in "natural selection" in this case and say "because this is done by humans, it's artificial selection," when artificial selection already has a distinct meaning.

[0]: https://en.wikipedia.org/wiki/Selective_breeding [1]: https://www.nationalgeographic.org/encyclopedia/artificial-s...