Yeah, I've never found a solution. Does the same thing for categories. You can't have two child categories with the same name, as in /parent-1/child/ and /parent-2/child/, WordPress just makes the second one /parent-2/child-parent-2/ so it looks to the search engines like search engine spam. Absurd. Completely different path in a real world, static html folder structure but WordPress can't find a way to fix it in their backend and seem to have completely given up on trying. It's completely counterintuitive and completely counterproductive for good SEO. WordPress, however, aren't interested in fixing it. It came up during some misguided bug report way back in the day. They "fixed" it by doing this. And now it stays. Functions that need to call a category should call the ID instead. It stays. We tell them it's whack, it's broken, it's not what we want. It stays. Whatever.