Still Fredo made a deal with Ola and Roth to get Mike to ease up on the "negotiations" for the "big deal" in exchange for something on his own. Maybe Fredo was playing both sides.
Well, I just don't see Fredo in any position (status or knowledge) to try and get Michael to ease up on the negotiations. Thus, you are probably right that Fredo did exaggerate his family position when he talked to Ola.
