Many of the theories advanced in this thread (and the other) show little understanding of how different flying aeroplanes is now, compared to how it was in the 1960s/70s.
Well there's only one theory proposed in this thread (though I share your view of it).
But in general, I think it does no harm to revisit previous accident investigations, with the benefit of hindsight, to see whether the lessons that should have been learned were or not.
Those who cannot remember the past are condemned to repeat it, as the saying goes. I certainly remember Staines well - I was working for BEA at the time (coincidentally on Trident major checks, so I know the type well).