The opinion creates a circuit split. It also is a big deal, since FSA credits and supervised release are ubiquitous in the federal system. As the opinion itself recognizes, "splits in authority are seldom so stark and consequential." So I wouldn't be at all surprised if and when the Supreme Court takes up a case to resolve this issue once and for all. (Assuming that Congress doesn't respond by amending the statute to make it clear.)
That said, for now, isn't Judge Mendoza's opinion pretty darn persuasive?