Of course there is. AJ is not a very good wrestler and a very mediocre striker. He is good at forcing the scrambles and going aggressively forward to cut distance, and at controlling his opponent on the ground. He is not a particularly well rounded fighter, but a very crafty fighter who works around his weaknesses to get himself to the positions where he is strongest.
Sean is an exceptionally good counter striker, who is long and precise. And his BJJ is actually very good, so it's not as if he is done if it hits the ground. He is dangerous for a guy who can be a bit sloppy moving forward, and has the length and reach to match Sterling. Also, people talk as time training didn't take place. It will have been a year or so since Sean last competed. His BJJ will have improved considerably in that frame, assuming he has been training consistently.
This is a much closer fight than people think.