I’m late to the party on this, but for the sake of completeness, here it is.
There are at least a couple of noteworthy items…
First, when combined with the UK judgement that “[p]ermission to authorise CW has probably been delegated by President Asad to senior regime commanders,” the US assessment suggests that Asad was not directly responsible for the 8/21 attack. In fact, it seems to suggest that the military stopped using CW in response to an order from higher up:
We intercepted communications involving a senior official intimately familiar with the offensive who confirmed that chemical weapons were used by the regime on August 21 and was concerned with the U.N. inspectors obtaining evidence. On the afternoon of August 21, we have intelligence that Syrian chemical weapons personnel were directed to cease operations.
Second, the assessment describes the government’s use of chemical weapons as a “coordinated rocket and artillery attack.” Most of the public USG assessments describe Syria’s missile forces, but have said next to nothing about delivery via rockets and artillery.