The black box should contain all of the crew actions relative to the engines, as well as any automated signal that the control elements received, such as fuel pump controls, etc. If the crew made an error, it should show up. For both engines to fail at the same time is very suspect.
Doesn’t this whole thing revolve around the term ‘fail’, that both engines ‘failed’ at the same time? There’s a difference between failing as in shut down or blew apart and not getting a response, or getting an unexpected response, when the throttles are advanced. Got to wonder if the engines were operating at all when they ‘failed’.
I know nothing of the damage to expect in a landing like this, but from the pictures I’ve seen of the engines, especially the left engine, the blades seem awfully intact for the engine to have hit the ground at 200 mph or so and have them spinning at any speed at all. Just an observation.