Some searches I come across redditmedia.com showing up in addition to reddit.com. Typically the results between these two are in fact unique posts, but it makes sense from a UI/UX standpoint for any redditmedia.com results to simply be reddit.com. Example search here.
It seems this results from certain upstreams having to index redditmedia rather than reddit.com.
EDIT: Literally seconds after posting this I remembered redirects exist 😅 , might still be looking into deduping these results to give a better default experience?