I feel like a right numpty, because everyone else on this thread has probably undrrstood this from the beginning
I only learned this recently, and in fact it had been driven from my mind by all the other 

stuff coming out.
This "computer assumed reliable unless proved otherwise" issue is desperately important, and rapidly becoming even more so as AI is inflicted on us (see DWP's new powers and plans, which is a whole other disaster in the making right now).
So cheers to @prh47bridge for reminding us all.