You misread their post. I too was confused until I had it pointed out how I (and you) had gotten it wrong.
Went ahead and quoted the post in full and bolded the relevant sections.
They were referring to Warsong Gulch, Alterac Valley, and the Elemental Invasions when they said “content unlock”.
When they said ‘time stamp’ they were talking about the exact time of day they would be releasing the BG content.
They actually made no promises or announcements about BWL and DMF yet.