No, we can't assume that.Here's a question I've never pondered until just now: can a lie be classified? If someone reveals information that would be classified if it were true, but the statement is fiction, would the White House be able to remove that content? Trump still doesn't want this book out, but it's apparently been thoroughly checked to not reveal any officially classified information. Should we then assume that anything said that could be classified is therefore inaccurate?
Something is classified or it is not; we can only really tell whether something is classified if it is tested. Thus something might be true, classified and published, basically because no-one checked or a mistake was made in the checking.
Bolton claims that the NSC has checked the material. If we take that as true, we should therefore assume nothing in it classified, or that it's sufficiently borderline that it was cleared when it shouldn't have been. Of course, the other issue is libel, so Bolton shouldn't say anything untrue that can get him sued.