In my experience, those polls tend use questions that are very poorly worded from the standpoint of the irreligious.

In this case, the full report gives the wording for the questions, and they seem fairly straightforward: "Do you believe in God or a universal spirit?", "How certain are you about this belief? Are you absolutely certain, fairly certain, not too certain, or not at all certain?", "Which comes closest to your view of God? God is a person with whom people can have a relationship or God is an impersonal force?", and

"What is your present religion, if any? Are you Protestant, Roman Catholic, Mormon, Orthodox such as Greek or Russian Orthodox, Jewish, Muslim, Buddhist, Hindu, atheist, agnostic, something else, or nothing in particular?"
INTERVIEWER: IF R VOLUNTEERS “nothing in particular, none, no religion, etc.” BEFORE REACHING END OF LIST, PROMPT WITH: "and would you say that’s atheist, agnostic, or just nothing in particular?"