This doesn't feel like vanilla unreliable speed to me. It may have been a contributing factor, but you don't lose control of a 737 doing over 300 knots in day vmc. You fly it level. Maybe you end up too slow and stall, but that clearly isn't what happened here. From the data it looks like a very high speed, extreme nose down attitude.
Either something mechanical has failed, or after a contributing factor, such as unreliable speed that has been mishandled, structural damage has occurred that has culminated in the final catastrophic dive.