I think that way too much is read into this idea of being 100% certain of something. The conflation of certainty with unreasoning belief is the basis of the frequent accusations that atheists are closed minded, or that we think we're omniscient, or that atheism is as faith-based as theism. But being sure about something, and being closed to reason, are not the same thing.
This may be easier to see when considering a more mundane question than the existence of gods. For example, I am 100% certain that Voldemort, as described in the Harry Potter stories (as opposed to some other person who has only superficial similarities, or who is merely named Voldemort, but is not THE Voldemort) is a fictional character, not an actual person. What this means is that I don't think there is any possibility of the Voldemort character being real. I am not on the fence. I am not "seeking". This does not, however, mean that I am closed to reason, or that I deem myself omniscient. If presented with credible evidence of Voldemort being real, I might become only 99% certain, or 50% certain, or even reverse my position entirely, depending on the strength of the evidence. Encountering such evidence would come as a complete surprise. I have zero expectation that any such evidence exists, and I certainly see no reason to actively hunt for it. But if it turns up, I'll consider it.