Mick - some possible explanations to your question:
You say the SI was clearly relevant - why was it? As it related to the FADEC which others had erroneously suggested was the definate cause!
To paraphrase "why would they say it flies like a Mk1?" - you could argue a Mk2 with a failed FADEC where you have to shut down the engine flies exactly like a Mk1 which has also had an engine failure. Engines do fail - aircraft must be able to be safe in such circumstances which are not rare.
I've no idea why it was not mentioned in the BoI, but perhaps for the reasons above it was not considered relevant? Who thought it shouldn't be mentioned? Is there any proof of that?
The main thing is - is it relevant? Doesn't seem like it had any bearing on the accident to me, but lots of readers of the times might now think so!
You ask why so many were certain the pilots were to blame? I'd suggest this is related to the balance of probabilities as to what happened - as discussed here this is quite a different to proof "beyond all doubt". I will go no further as it is not good form and the thread will get locked.