I dont think he said the 'fight in a heartbeat' comments due to it not being a reality at that point. I think he said it out of confidence at that time and rightly so. He knew he is one the best MMA fighters in the world and has all the physical tools to fight any style. What really bothers me is that when it became a reality he chose a cowardly path and went back on them words especially fighting a unprepared MW disadvantaged Sonnen.
I definitely think it was because it not being a reality.
He said "in a heartbeat" because he thought there was no way he would have to fight Chael in a heartbeat. He probably felt if he EVER even did have to fight Chael it would be when he had a full training camp to focus on Chael.
But when the "In a heartbeat" moment came he backed down using the worst excuse i have ever heard a champion use.
The guy is obviously a mental midget. Because if Dana or Greg or anyone could have forced Jon Jones to step in to that cage i think he would have performed just as well as ever and shown why he is one of the best. Instead he was too insecure in his own abilities to try. And honestly i find it sad. The guy is a child in so many ways except physically.