Thanks for the training links. Seems he was upping the threshold doing specific sustained aerobic work in the mountains. And, as he has stated himself on a training video, another focus of his has been lowering the glycolytic system's ("anaerobic") contribution to power, and doing those rides addresses this too.
Thing is, that focus pretty much means losing the kick unless you won the genetic lottery two, three times, or more.
Sprinters that excel in time trials are as rare as TTists that win bunch gallops. Putting it bluntly, the anaerobic system must be trained to favour either end, sustained power or sharp power.
Wout is obviously very talented but this is too good to be true.