I agree with wiedehopf, AGBagb, and others above that it really shouldn't matter WHY the system is behaving or even exactly HOW, the crew's job is to react to what is happening and regain control. It's not exactly rocket science, pull and trim until you get the attitude you want. By concentrating on the precise nature of the failure we risk missing the fact that there are many ways in which the behaviour in question could arise. The THY accident at Schipol is a case in point - much was made of the single Rad Alt failure which ensured the thrust levers remained closed, and I believe the system was modified later, but there are many ways the AT might have failed, and if the crew had been monitoring their energy state properly they should have coped with all of them. Boeing will have to answer for their questionable judgment writing the FCOM, but they weren't on flight deck, the crew were.