But it was talked about in the past tense, ie this is the statement that was released at 12.30, as the PP says, when she was most likely still alive.
They obviously knew that it would likely be that afternoon though, which is the information they passed on to those who needed to know, the media, government etc.
The public did not need to know, but as others have said, this was pretty obvious anyway and hinted at, from the widespread wishes from foreign leaders to the media commentary stating how unprecedented the original statement was.
So no, we weren't lied to, we were given (likely correct) information at the time of the original statement, then not updated further until the death announcement. But we were told as soon as possible, once all the necessary arrangements had been made first.