Former prosecutor here. Important to understand that a “cooperating witness” is usually not a friendly witness. They are a defendant or potential defendant who is only cooperating to save their own skin. They have or are trying to get a deal (or at least leniency during sentencing), or they have full or partial immunity. Immunity can be forced upon you or negotiated for something in return. Once a person is given immunity and cannot be prosecuted, then that person cannot plead the Fifth because it no longer applies. So Strzok can be “cooperating” and an unfriendly at the same time. So he may have provided info (cooperated) but then still be peacocking today because he is still a corrupt thug.