Badges, Badges, oh my!

Ask Discourse tells me that only actions in public categories count towards badge attribution. Is that correct? If it is the case, then it means that for a “public” community where most of the activity is going to happen in private categories (see Public community, private community, or a mix? (context: migrating from Facebook) ) then basically, badges become kind of nonsensical.

Would somebody be so kind as to clarify this for me? Thanks in advance!!