This right here ^. It sounds as though the sanctions would be less severe due to disclosing it, but the fact that he hasn't been sanctioned at all yet... could be bad news. He has less than 3 months until competition, so if there's a sanction longer than that, he's screwed.
Overall, I doubt Brooks lied. It's pretty easy to get a TUE for stimulants from what I can understand (whether he needs it for studying or competition); he probably was just being an idiot. Will probably be up to if WADA is lenient on idiots and whether or not they believe it gave him any advantage.