I think you will find that the SI report is available to the Coroner. It forms part of the evidence. The witnesses are there to expand on the evidence. It is only publication to the wider public that is withheld until the inquest is complete.
Yes, it is available to the Coroner. But not to people who would actually know what questions to ask. Please note, that in all the similar cases of attempted cover-up discussed here (Nimrod, Chinook, Tornado, C130, Sea King etc) it is members of the public, not MoD staff, who have revealed the truth.
The witnesses are required to state the truth, the whole truth and nothing but the truth. That means they are not to mislead, by omission or commission - which is on a par with perjury. In all the above cases, MoD did. You've got to admire their consistency.