The NSFW blur is sometimes not applied correctly. For example if you have turned on displaying Avatars (or Magazine icons) then those elements are blurred instead of the post preview itself - at least that's my experience on Vivaldi browser. Styling might be interpreted differently on other browsers. And sometimes it takes a second to apply the style (I think after page reload) so if it's high up there on the list one might still see NSFW content unblured.