The Memo references an addendum, which isn't included in the link. The addendum is public, except that it is heavily redacted. The addendum supposedly details Flynn's cooperation, but since we don't know what it says, we can't draw any conclusions one way or another.
Except that isn't entirely true. We know that Mueller's team will declare plea deals void if the defendant doesn't cooperate (see Manafort, Paul). Flynn got a very favorable recommendation. He was looking at potentially five years for lying to thee FBI, and the government essentially told the judge it doesn't care if he gets -0- prison time because of his cooperation. So, whatever he cooperated on, the government is satisfied.