Do these /deprecated/... destinations just redirect to the new version of the page?

I end up at /language and /libraries when testing the old source for each. I think I see it jump to /deprecated first though. Just checking that that's the intended behavior

Yes that's the intended behavior if you don't specify any fragment (#id).

It's been a while since we implemented this, but remember we set up client-based redirects to redirect from a fragment to the correct location. As different fragments should lead to different pages, but the server doesn't see the fragments.

For example, /guides/language/language-tour#enums will redirect to /deprecated/language-tour#enums, then the JS on that page will look at the fragment and redirect to /language/enums.