Going back to the original question:
Several changes were made to the BSA’s youth protection policies in late 2018. The Scouting Magazine article that you found was published prior to those changes.
Under the old youth protection rules, 2-deep leadership meant:
Two-deep leadership is required on all outings. A minimum of two registered adult leaders — or one registered leader and a participating Scout’s parent or another adult — is required for all trips and outings. One of these adults must be 21 years of age or older.
Under those old rules (no longer in effect), a parent of a participating Scout could be used as the second adult. A registered leader age 18-20 (for example: Assistant Scoutmaster or Assistant Den Leader) could also be used as the second adult.
Under the current youth protection rules:
Youth Protection and Adult Leadership: Scouting’s Barrier’s to Abuse
Adult Supervision[2-deep leadership section] Two registered adult leaders 21 years of age or over are required at all Scouting activities, including meetings. There must be a registered female adult leader 21 years of age or over in every unit serving females. A registered female adult leader 21 years of age or over must be present for any activity involving female youth. Notwithstanding the minimum leader requirements, age- and program-appropriate supervision must always be provided. (Youth Protection and Barriers to Abuse FAQs)
All adults accompanying a Scouting unit who are present at the activity for 72 total hours or more must be registered as leaders. The 72 hours need not be consecutive.
[No one-on-one contact section] One-on-one contact between adult leaders and youth members is prohibited both inside and outside of Scouting. (Youth Protection and Barriers to Abuse FAQs)
- In situations requiring a personal conference, the meeting is to be conducted with the knowledge and in view of other adults and/or youth.
- Private online communications (texting, phone calls, chat, IM, etc.) must include another registered leader or parent.
- Communication by way of social media (Facebook, Snapchat, etc.) must include another registered leader or parent.
So two BSA registered adult leaders age 21+ are required for all Scouting activities, including meetings, with some limited exceptions as described in the Youth Protection and Barriers to Abuse FAQs. Other adults (YPT trained or not) no longer count as the second adult for 2-deep leadership purposes.
