Expected Behavior:
When adding a new party member to a Group, the new party member’s Content Sharing (CS) setting will inherit from the Group’s CS preference. If the Group has CS turned on, the player will have CS turned on when their request to join the group is accepted.
Actual Behavior:
When adding a new party member to a Gorup, the new party member’s CS setting is turned off.
Thanks for reporting this! This is how it was designed, so you don’t find yourself sharing content with someone without realizing it. However, I have passed along your expected behavior, for the team to review. 
I can understand that. The “Actual Behavior” I’d expect if the Group CS setting is turned off. (Again, the player CS inheriting from the Group CS setting.) Thanks for passing along the feedback.