Two-level gated. First, admin must grant the user account access (whatsapp_group_participants_enabled, from the admin panel). Once granted, the user must also enable group_participants_enabled on the specific instance (from that instance's settings) — this lets a user with multiple WhatsApp Direct instances opt in per instance rather than all-or-nothing. Only works for a group the connected instance is already a member of. WhatsApp only reveals a member's real phone number to you when it's already resolvable (e.g. an existing 1:1 chat) — most members in larger groups are protected by WhatsApp's Linked ID (LID) privacy feature and will come back with phone: null. This is a WhatsApp-side privacy protection, not a bug — see summary.note in the response.