The BBC is not confusing its viewers, since depending on where you watched Doctor Who last week, you would have heard two different start times.
On BBC1, Doctor Who is airing at 6:30pm. At the same time, BBC2 will be finishing its live coverage of Match of the Day.
On BBC-HD, which shows the "best" of all four BBC channels, the live Match of the Day coverage starts at 5:00pm and continues to 7:15pm. Since Doctor Who is pre-recorded, it can be shown later on the HD channel, which makes sense, since I can't imagine the BBC (or any network!) stopping coverage of a live sporting event to show a pre-recorded program that can be shown later.
After Match of the Day, BBC-HD are showing the latest episode of Over the Rainbow simultaneously with BBC1 (from 7:15-8:25pm). Doctor Who will be on BBC-HD after that.
So, if you watch Doctor Who on BBC1, it starts at 6:30pm. But if you're watching on BBC-HD, you'll have to wait until 8:25pm.