Why do some Lemmy community not show up in magazine search (others on same instance do)?

Yesterday I learned about https://lemmy.ca/c/ontario_community_directory (edit: I got a wrong link somewhere -- this one should have been https://lemmy.ca/c/ontario_index) and my local city sub of https://lemmy.ca/c/waterloo. I can't find them in magazine search (eg, https://kbin.social/magazines?q=waterloo). They're not brand new (several days).

If I visit the URL I expect them to have (eg, https://kbin.social/m/waterloo@lemmy.ca), I get a 404 and no option to subscribe (I heard some people mention before how Lemmy would show empty communities until the first person on your instance subscribes -- not sure if that even applies to kbin and I can't seem to subscribe anyway).

I can see other subs on the same instance. The whole reason I learned about these subs is because I can see https://kbin.social/m/ontario@lemmy.ca fine. So it doesn't appear to be the instance.

Anyone have any ideas what's wrong and how to fix it?