He closed the gap solo because he didn't have the power to follow in the Kemmelberg. Which shows that he is not in top shape. Even Asgreen rode faster than him there and he also seemed a bit gassed.Lampaert closed a gap to the favorites, solo, after the last climb. He might not be as good as Bettiol, or Pedersen or van der Poel... which is why he gets less stars. And he's much faster than you think. He could possibly beat Bettiol, Küng, Benoot, Van Marcke, Teuns, Andersen in a sprint, maybe even Sénéchal depending on the race. Basically any rider who never won a bunch sprint.
I don't think he is faster than I think. Apart from that being quite an axiomatic statement, I really don't see why Vanmarcke shouldn't also be able to beat anyone of those you mention. Apart from Kragh and certainly Sénéchal (are you kidding me there?).