Letters of recommendation

The guideline from Chicago Booth regarding second letter of recommendation:

"The second letter can be professional in nature or from an organization, club, or volunteer project with which you are associated. These letters can give us a different perspective of your skill-sets outside of your professional environment. There is no preference on who supplies your second letter of recommendation; our only guideline is that it should add new and valuable insights to your application".

What do you guys make of this? Although the prompt does not necessarily say so, but does the Adcom prefer the second letter from someone outside of professional environment? I mean even a professional colleague could sprinkle a few instances of my work outside of the professional setting.

Thanks.