Only partial federation of hashtagged posts to Kbin microblog?

I've been looking for a usecase to see where the combination of Threads and Microblog was particularly useful, and with the news around the potential superconductor #LK99 I figured this would be an interesting test case. So I made a magazine on kbin.social for LK99, and added the hashtags to tags in settings.

But now only some tagged posts show up under microblog. So it does work, because otherwise 0 posts would appear. But if I search on mastodon.social for #LK99, I get way more posts, and only about a third of them show up on Kbin.

Its probably something to do with federation, but I'm not really sure where it goes wrong. Interestingly, even some posts that are made on mastodon.social that are correctly tagged do not show up on kbin, even though other posts from mastodon.social do. I even made sure to follow this account with my mastodon.social account to guarantee federation between the servers.

Anyone has an idea how this works? And if there is a way to force more of the posts to show up?