WRT the M B witness' "I don't know, I wasn't there"....
As others have hinted (or maybe i read something into it)
the man works for MB
MOD is obviously an important customer
there are other Bang-seat manufacturers
anyone in MOD who may bear a responsibility for poor systems/safety procedures, may also have influence in specifications for purchasing.
To put it bluntly....the MB staff are going to be somewhat circumspect when it comes to rocking the boat...they are unlikely to deliberately cause a major embarassment to one of their major profit-sources.
Motor-car seat-belt mountings, by numbers, have far more events than bang-seats...one does not hear of fatal crashe caused by seat-belt failure....where fittings have to have movement, there are stepped bushes / shouldered bolts/ spring-washers /fibre washers to ensure that, according to design and purpose, a belt can be removed/checked/refitted by a relatively unskilled person
yes, some designs have a very thin head on a stepped bolt...they get dogged-up tight...if the retained part is meant to move, it does..if it's meant to be rigidly fixed, it is.
there's a whiff of arse and back-covering here, IMO.