To the best of my knowledge, this doesn't happen at all. Published post slugs don't get altered automatically by any process.

Now, you might see this behavior for *drafts*, because a draft isn't published yet and hasn't had its slug finalized. But when a post is published, the slug is saved as part of the post in the post_name column, and it doesn't get altered unless you manually alter it.

I just ran a quick test and published test-post and test-post-2 (both titles were "test post"). Deleting the first test-post didn't alter the slug of the second one. Nor should it, I'd think.