Mine says, "default... A preselected option adopted by a... mechanism when no alternative is specified..."My dictionary states "default ...a failure to fulfill an obligation or to appear", so yes, I would agree that if the gods don't show up, no belief in gods would be required. And there must have been thousands of years of evolution before the awareness of, or creation of, in my opinion, of deities in the minds of humans took place.
What you're suggesting is that the option to disbelieve in gods was preselected by... some... means. I reject that.
I don't believe in Fate.