At G-W his main weakness was tactical. He did more work than any other rider, and still dropped everyone except one rival who has a better sprint than him, and had more to prove. Definitely not van der Poel's best race, but with bigger goals a week ahead it's hardly something I'd be concerned about.
As for CX, I don't think that he was at anywhere near to a peak, especially after kerstperiode, nor does he need to be in that discipline unless Wout is racing with 100% commitment, which was not the case this year nor is it likely to be in the future.