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...