It's not clear to me what you mean by "they don't overlap at all". If I create a truth table for the two binary possibilities of 'leaked?' and 'created?', I get something like this:

    Created, Leaked:  It was created in a lab, and accidentally got out.
    Not Created, Leaked: It was being studied in a lab, and accidentally got out.
    Created, Not Leaked: It was created in a lab and deliberately released (the biowarfare hypothesis.)
    Not Created, Not Leaked: The lab had nothing to do with it at all (the wet market hypothesis.)

Created/leaked are independent, but since both or either could be true or false, there seems to be 'overlap.'