Re: "But the train did come to a complete stop just 7.5cm from its intended stopping point"
" In reality, they'll either be skilled enough to drive the train or they won't."
The ideal aircraft cockpit crew is composed of a man and a dog. The Man's job is to take the controls if something goes wrong with the automation and the Dog's job is to bite the Man if he attempts to take the controls
The reality of human supervision of near-perfect automation is that attention wanders, people get bored and start doing other things than what they're supposed to be doing
It's probably better to layer extra supervisory monitoring systems in (dumb ones with simple tasks) that will stop the train if things go amiss (including constant online montoring going offline) and have sufficiently trained staff onboard to be able to drive in "limp home mode" to the nearest safety point from there if it can't be done remotely (we're at or nearly at the point where "waldoing when required" is feasible around most of the world and definitely so in places like Japan)
At some point, actually HAVING humans continuously in the loop _is_ the most dangerous part of the whole operation and your safety systems have to be designed against bored&redundant people fucking around or falling asleep