Discovery decides who you see and who sees you, so it is worth being plain about what goes into it.
What we use
Your birth date puts you in a Tribe. Your interests and the languages you speak decide which people inside it surface first. Nothing about your contacts or address book is involved.
What you control
Every input above can be narrowed or switched off in privacy settings, including whether you appear in discovery at all. Blocking is one-directional and permanent until you undo it.