Sounds like pilot ewrror to me, too, Adler, but I don;t have the detailed data that you seem to have. Missing your target speed by 34 knots is very stupid.
Maybe it will come out that they had set autothrottles but failed to verify they were working or perhaps they worked until some point when they stopped working. To me, that's the BAD thing about computerized aircraft. Everything is fine until it isn't, and thenm everyone second guesses you. If that is the case, why not simply fly it manually and at least you'd be monitoring it ALL the time instead of havong your attention elsewhere when it malfunctions.