I don't know how the civilians figure mishaps rates but two items come to mind here.
One - until the **FINAL** release of the investigation is out......nothing is certain except for the unfortunate outcome
Second - at least in the military.....absolution from a Class A mishap can be granted under certain circumstances.

I had the same thought as you when I walked down one squadron's passageway and saw a recent 50,000 Mishap Free Flight Hours Safety plaque on their wall and knowing full well that they had had a Class A FM (flight Mishap) with loss of airplane and pilot

Of course the other possible answer is that they have an IT department that is little behind the 8-ball and hasn't gotten around to updating the website yet. The bosses have more pressing matters to attend to at this time.

USMCFLYR