I can't explain why it seems to be news to the SI though
On the two occasions I've had to submit evidence to a BoI I was initially gratified they had asked the correct person (as I held airworthiness delegation on the subject kit).
On the first occasion my evidence was omitted entirely because the RN did not fancy embarrassing a senior RAF officer well known to this forum. In short, the evidence was a subset of what I submitted to Haddon-Cave 20 years later, which he characterised as "savings at the expense of safety". No one died in that one.
On the other occasion (multiple fatalities) my evidence was essentially the same, although specific to that aircraft type. This time, regulations implemented properly, but then over-ruled by a non-engineer behind our backs. Again, the BoI report was rendered complete nonsense by the omission, and today MoD deny the investigation took place or my report ever existed. A copy was submitted to the Defence Committee last month.....
I fully accept Courtney's assertion the SI did a good job, given the constraints they were under. I'd just love to see their unedited report. I always suspected what happens, but during the MoK Review it was a real eye-opener seeing the sheer scale of changes made to the CHART report. It isn't often you get to see the original. What they eventually released still said the aircraft wasn't airworthy, so imagine what the original said! ZA721 (FI 1987) was the same. The AAIB were apoplectic over what was omitted. What would stop such interference?