I don't know the route for the U23 (length, climbs), but he is always there when in the final and copes a lot better with a hard race than many other pro sprinters (i'm inclined to say, better than most). Had a staggering amount of top 10 finishes with the pros (i think over 20), he's just lacking in top speed. If he can manage to become faster, a lot of those top 10 finishes will turn into wins. Or maybe he'll just turn into an allround classics rider? I don't know if there is anybody faster in the U23 though. He easily beat Groves yesterday, and he's said to be one of the fastest.
And if Foss (22) can win l'Avenir at his age, Philipsen (21) shouldn't feel bad about riding the U23 WC.