EAP86 is right, HSE state the case is subjudice, so will not be releasing the finer details of the charge. They have declined to comment on what evidence they have rejected/accepted, and why, but they have firmly stated that MoD is in the clear; so it is pretty obvious (a) they haven't read the evidence, and (b) they think they have something else that has not been discussed.
Some PTs relied on industry for integration of engine/airframe/seat but others didn't. I'm not sure whether ADRP gave any thought to how this might complicate matters. It could certainly complicate how external parties view the question of who was responsible for what.
I'm not sure what input ADRP had to this on ejection seats, but they had none at all on avionics, and their integration with each other and aircraft, as the policy was issued, and managed at all DAs, by the same single section in MoD(PE). Until June 1993 that is, when the section was disbanded, without replacement, the mandated Def Stan cancelled (but which remained mandated for another 15 years), and the work, if it was even carried out, became a minor task to hundreds instead of the core task of a handful. Hence the variable approach you mention.
Some might recall the Bernard Gray report, commissioned by the last Labour Govt and then picked up by the Coalition. It is why he became MoD's procurement boss. Gray trumpeted this around the media and suggested a return to this old regime, but it turned out he didn't actually know it was an old policy, and it appears one of his lackeys cut and pasted a few pprune posts in a briefing. (Not a bad strategy, but it helps if you do some research before presenting the posts as your own work). When asked about this by a Minister, MoD denied Gray had even mentioned the subject, despite his interview still being available on the Radio 4 website. My advice to MoD is swallow your pride and get some consistency back into your work.