Follow-up for protected workflow tutorial

These follow-ups from Tutorial: Build a protected workflow for your p... (!123872 - merged) should be addressed:

• @aqualls started a discussion:

  • !123872 (comment 1451570594) suggests changing the branch naming to release/v1.*.
  • !123872 (comment 1461072983) explain why top-level groups are private. It didn't make sense to me either.
  • !123872 (comment 1451570510) and !123872 (comment 1451889277) describe a different nesting approach for the groups and sub-groups. !123872 (comment 1452660818) contains a visual aid for the nesting, and I think one's especially worth including.