Every time you hear about Hillary being the “Democratic nominee” that is actually false, according to the DNC itself. Super delegates don’t vote until July 25, and as it is now Hillary doesn’t have enough delegates. That is why there will be a contested convention.
This “transitioning phase” is part of a multi-pronged approach to the present Clinton crisis. This is being done to both mislead the public and donors, who just got leaked, as to everything being a-ok happy happy fun time, but also for the highly unlikely event the email scandal disappears, or if Sanders and his global movement drops out of the picture.