Think of the category name as what the browser displays on the page and the slug is what is in the URL. Ultimately, as long as the category ID is the same, the link will go to the right place even if the slug is outdated.
This is the actual URL for the support topic
https://meta.discourse.org/c/support/6
And this will redirect you back to category #6, regardless of the slug:
https://meta.discourse.org/c/definitely-not-a-real-category/6