Flying together should not be a cause for surprise anymore.
Flying together isn't necessarily a surprise, but that's not what is being challenged.
There are two reasons why imo this picture is not worth our time.
1: The picture probably isn't real to begin with.
2: Even if the picture is real, who cares?
We know that the PLA is doing MUMT testing between manned aircraft and unmanned aircraft, but that kind of testing doesn't require the manned aircraft and the unmanned aircraft to fly alongside each other in the same formation. If anything it is far more relevant and impressive for MUMT testing if the unmanned aircraft is a long distance away from the manned aircraft. Furthermore, even if the picture is real, we also can not rule out the possibility that the unmanned aircraft is being controlled from the ground rather than the J-20 or flying with extensive autonomy.
If this picture is real, it would only be noteworthy by being a rare image of GJ-11 with a concealed engine nozzle in flight, and noteworthy seeing GJ-11 and J-20 close to each other in formation as a "huh neat acknowledgement".
But there's not much else that is interesting here, even if the picture is real, imo.