Since Michael already knew that Frankie Pentangeli was alive and was being prepared in custody to testify against Michael – the committee's surprise star witness - my take, arrangements would have been already put in place to bring Frankie's brother, Vincenzo over or “Vincenzo was already on a plane to the hearing” when Michael went to talk to Fredo

I agree knowing about Questadt helped [not pivotal] confirm Michael arranging to bring Frankie's brother, Vincenzo over, was Ace! thus trumping “Roth played this one beautifully”

Let's say if Fredo had not said -
1. They [Senate committee] have got Pentangeli
2. Questadt belongs to Roth

thus not revealing how deeply Fredo was involved with Roth and Ola, against Michael that Fredo withheld the said information because Fredo still wanted to harm Michael and try to send him to Prison -
  • Would the outcome been any different?
  • Michael may have given Fredo a pass even after Fredo's stepped over outburst [Michael still should have! no matter what]