Content a user has access to in SharePoint Online via a Office 365 Group is security trimmed from Search
When sharing content in SharePoint Online, the sharing interface allows a user to type the name of an Office 365 Group. SharePoint Online content that is shared in this manner will not appear in SharePoint Search results to the members of the Office 365 Group. This doesn't provide a consistent experience for users, as many users may not be aware what entries are Office 365 Groups, Azure Active Directory security groups, etc. We'd like to see content shared to the members of an Office 365 group in this manner appear in the search results for those users.
This is important as we are expecting that AD security groups created by Office 365 Groups will act just like any other security group. Otherwise, it is just plain confusing.