They wanted to avoid another entrance/exit on screen to keep us guessing how this Star Trek Inception works.

I understand the reasoning from a suspense perspective but manufactured suspense does not feel suspenseful. Think about it: why show the entire long debate about leaving or not if none of them actually care? The only thing that makes sense is that once they understood the danger was real there was an off-camera conversation with Pike or Una wherein Pike or Una presumably told them that the danger was acceptable and to proceed. But if we accept that the conversation happened off-camera, then the presence of the debate scene doesn't make sense from a storytelling standpoint.