The AAIB report is not the result of an investigation, but a simple statement of the event from the captain.
Correct.
And the AAIB is, of course, at liberty to follow up any event brought to its attention with an appropriate level of investigation, ranging from telephone contact with the personnel involved to a full field investigation, and to make any safety recommendations it considers necessary based on its findings.
Clearly it didn't consider that any such action was required in this instance, unless anyone is suggesting that there are additional facts it was not made aware of ?