Mueller’s team appears to have no doubt that Manafort was lying to them. That means they didn’t really need his testimony, at all. It also means they had no need to keep secrets — they could keep giving Manafort the impression that he was pulling a fast one over the prosecutors, all while reporting misleading information to Trump that he could use to fill out his open book test. Which increases the likelihood that Trump just submitted sworn answers to those questions full of lies.
And that “detailed sentencing submission … sett[ing] forth the nature of the defendant’s crimes and lies” that Mueller mentions in the report?
There’s your Mueller report, which will be provided in a form that Matt Whitaker won’t be able to suppress. (Reminder: Mueller included 38 pages of evidence along with Manafort’s plea agreement, which I argued showed how what Manafort and Trump did to Hillary was the same thing that Manafort had done to Yulia Tymoshenko.)