I think the author is embellishing. While it may be trickier than driving a truck, this is not on the same scale of difficulty as operating a large freight train, where the operator needs to consider where the back of the train is in relation to the locomotive, nor as difficult as operating an airliner, where a momentary navigational error could put the entire airship underground in a matter of seconds.

I'd expect that trainee engineers are trained on specific routes. Whereas a car or truck driver would be expected to operate safely on roads they've never encountered before, this should not be the case for a passenger train engineer. So the difficulty would be doubly embellished.

It appears to me that the most difficult part about driving a train is remaining alert and sober, absorbing and executing the restrictions on the track, and doing so confidently well in advance of turns or restrictions. The theory presented in the article, that he was injured as a result of a rock throw and lost control of the train, seems like as good a conclusion as any. Especially given how unusually dedicated the purported evidence shows him to be.