That’s what happened 2 years ago when Kristoff and Degenkolb went 1-2 on the Champs. All the pure sprinters had been burned off in the mountains, so it was a couple of hard edged veteran classicomanos who fought out the big win.
It makes a certain amount of sense that teams with an appropriate rider might look at the stage and think a later attack is the way to go, once whichever of Bora and DQS ended up chasing started to tire. But that can’t be the case for many teams. So yeah, who knows what they think they are doing
You say "Sunweb.' It's actually just Roche. Shots of Hirschi and Benoot et al sitting at the back of the peloton. Honestly no idea what Sunweb are doing, but they've known better than I for most of this Tour, so I won't question it.