We're not talking about a random teammate, we're talking about Evenepoel, with the assumption that he will be in good form. If he isn't, nobody will oppose the idea of him fetching bottles instead. When they send Evenepoel up the road at a moment when everything starts falling apart and every team has to assess their situation, alarmbells and sirens go off all over the place. That means rivals have a choice to start working immediately full gas, or ride for 2nd place. We can make fun of Evenepoel during the WCC, but him going in the attack and the Italians missing the break, was basically enough to knock them out.
The presence of Evenepoel is in favor of Alaphilippe and the other way around just as well. Alaphilippe may not be Van der Poel or Van Aert in terms of sprinting, but he's still enough of a threat that nobody wants to drag him along for a free ride. That means chasers will think twice about going all in after Evenepoel. On the other hand, they know they can't give Evenepoel as much as 30 seconds so they'll have to drag Alaphilippe along if they still want a chance to win.
The premise you are insisting on is completely irrelevant as well as ultimately imaginary. What does it matter that Alaphilippe is supposed to be "super-leader" above Evenepoel, when they would both race differently and when Evenepoel does his thing and is successful, he would win. He's not going to squeeze his brakes 5m from the finish, waiting for Alaphilippe to win the sprint.
Besides, if Alaphilippe is strong enough to drop all rivals, as you suggest, he is free to close the gap in case Evenepoel would be up ahead.