Yes I don't understand that. The timeline matches up with Jones even. Several weeks before the event, they randomly tested Lesnar. A week or two before, they tested Jones. Jones' came back just days before the event and was pulled. Lesnar's came back a week or so later.They didn't withhold anything, the test results just weren't back until after UFC 200, which is typical based on the testing date and the results date.
You could argue that the exemption was bad, but they've since changed that.