I am using a search query to research some Twitter data and would like to get some additional metadata beyond what is normally available. For example, the information about the date the user account was created does not appear to be included. Is there a reason for this, or a way of obtaining this?
That information is not a part of the Twitter metadata payload. Changes along those lines would need to originate with the Twitter Boulder development team. A change like that would probably be non-trivial for a system the size of Twitter.