I’m blocking probably hundreds of mags (all mags on Cloudflare sites like lemmy.world). The results of search queries are rich in posts from blocked mags. When I visit the post the sidebar shows that indeed that mag is blocked.
Note that if I simply browse the main timeline, the blocks work as expected.
I would normally report this to the kbin bug tracker but Codeberg deleted my account and it’s hard to create a new one.
Fedia runs Mbin at the moment, not /kbin, issues can be reported on github
but assuming you may not have a github account or posting via the fediverse is easier, you can also try posting mbin specific, non-fedia instance questions, comments, or concerns to https://fedia.io/m/Mdev@kbin.run