UPDATE: SharePoint Online team sites + Office 365 Groups moving beyond First Release

Please can someone help detail the search story for Office 365 Group Team Sites.

Currently, it appears that only 'Public' O365 Group Team Sites have contents indexed by the SharePoint search index.

'Private' groups do not.

You can test this by going to a 'Private' O365GTS document library and search for a document using the search box on the top right.  I get no results.

Searching using the search box on the top left of the 'Home' page gives results (Office Graph Search?)

Is there is a way to have 'Private' O365GTS contents indexed by SharePoint Search? Please can someone point me in the right direction...  It is not a good story for users to not have documents show up in the SharePoint search center...