I guess Bayless was talking about the famous Hershel Walker trade and said that Jimmy Johnson had told him several days before the trade happened that talks were in progress about the possible trade. That was back when Bayless covered the Cowboys down in Dallas, and he was trying to make it sound like he had such great connections that the coach of the Cowboys would confide in him.
A day or later, Jimmy Johnson tweeted the clip with the heading, "This never happen."
In other words, Bayless lied, unless we really want to think that Skip freaking Bayless' words are more credible that Jimmy Johnson's. Johnson is a legendary HOF coach, and Bayless is a brown spot on the dirty carpet that is today's sports media. No doubt in my mind who is more believable.