From user testing sessions at RightsCon 2018 (pp. 38-39):

Issue: The lock icon on the not-shared folder (indicating that it’s private) was interpreted by several respondents as meaning something else than was intended; namely, that it is secure or encrypted, or even that it’s locked in the sense of inaccessible, requiring some key. The lack of a lock on the shared folder adds to the confusion

Suggestion: Remove the lock from the icon.