Not all train accidents are listed in that page.I am having difficult time to figuare out whether you are just making this up or simply everyone else just don't care whether there was one such accident happened in Korea.
Yes, both KTX and Shinkansen have had auto collisions before, no train to train collision in service. The KTX train to train collision happened at the maintenance depot where the PTC was off and no one was injured.
Wenzhou accident was due to adminstrating human error rather than a system malfunction. You are right on this that this kind of accident should not happen at all.
It was a system error because the lightening strike caused the PTC system to malfunction(Railway equipment are supposed to be lightening resistant but this Chinese produced equipment wasn't) and the controllers decided to disable the malfunctioning PTC to move the traffic, which led to the disaster.
Derailing does not cause the train to fly off the viaduct because the jacobs bogie used in KTX I && II locks up the whole train set as single unit, and the other cars on track hold onto the derailed unit.Like KTX never derailed. Oh wait it did, but there had to be a viaduct for it to be frown off from when it was derailed, but since it happened in a tunnel so where could it flown off to.