Well said. ^
The thing to remember about the sprinters is that they are doing a 100yd dash at the end of a marathon.
The best 100yd dash guys are the track sprinters. Who would crush your Ewans, Philipsens, Cavs, Sagans, Merliers, etc. in a sprint every day and twice and Sunday. But probably not at the end of a 150km stage. And none of them would make the time cut on a mountain day.
The grand tour sprinters and almost to the same degree the one day race sprinters can run a marathon within par and still bang out a sprint that none of the better marathoners can match.
Yes, they train for the marathon. And the sprint.