This is pretty interesting..as it has never happened before, I think for a "normal" fight/fighter coming back from "retirement" he wouldn't have fought until 4months after because he'd have to have been tested by USADA, as I understand it, that paragraph is so you can't skip testing by "retiring" every other week and applies to UFC fighters for who USADA is working for..so if you come from say King of the Cage, ofcourse you wouldn't be expected to have USADA testing, Brock did fight in the UFC however, and according to people explaining how he came back for 200, always was and will be a UFC fighter (unless he gets released), which means that he should've been tested or given a 4month notice.
Curiously, the negotiations started 3 months ago (according to Brock himself), while the first instance of USADA testing happened last friday or something (per twatter). You'd think an org that takes PED use seriously would've included some testing in the negotiation process, but apparently not.