You may have access to better data (or your AMD sources is giving you a AMD-centric spin on that 80% success rate, since we don't actually know what constitutes 'success').
When THG first reviewed the 960T they mentioned a 37% success rate as reported by Asrock. Those were early days but THG reviewed a 960T not supplied by AMD.
THG: Turning Zosma Into Thuban
I might be overly cynical but it's hard for me to imagine AMD turning a perfectly good Thuban into a Zosma and lowering the price 30%
just to meet demand for a X4 part that a X4 965 could fill. The 960T would have been the lowest binned Thubans in any case. Missing TDP / VID targets, or defective/problematic CPU cores, all the usual things Zosma owners might have to deal with. Those with a 'golden' 960T are going to be sure to mention it. Those that didn't get one? They tend to be less forthcoming.