E3 Harelbeke has really a very limited effect of cobbles, just the cobbled hills. And Degenkolb is a sprinter that can climb those hills as we've seen already, so that's not a good excuse.
Degenkolb is the only one winning races with ****ty fields, not Boonen. So I don't understand your logic there.
Sprinting speed isn't even affected all that much by form. Your freshness at the finish of a rather hilly race is however affected by form. All the top sprinters win races in March and April.
Do you really think Degenkolb doesn't want to be good for the classics? I'm sure he rather peaks for the Tour de Picardie according to you, but that's another matter.