Moreover, the first comment on that page points out that the self-threading needle is ill-suited for typical sewing because the eye is so big. And the side-threading needle in the article seems to have an even larger eye.
I think the article says it has been done before but that the previous version had too wide a gap, and possibly a different morphology, and so the thread would slip out.
This appears to be a rediscovery of an old invention in that case, so presumably a patent won't be granted.
I guess most people have thought about it but probably thought, there probably is a reason for this.
Just goes to show, never assume things can't change.