You are missing what he stated. He stated that his science would yield a possible date range. His science doesn't really contradict the first bug guys because their dates are still within the range he gave.
Its just that this guys science doesn't lend itself to a precise date like the bug guys did.
My reply to another poster was about DW's need for an alibi for 1/31. It was not about whether 2/2 was in the range or close to the range given by this witness. You are misstating what I posted.