While the scenario is likely real, I suspect the video are compilations of separate clips/events.
The part where they engage simulated opfor with datalink from AEW&C is also not very clear -- needless to say, being cued to a target by a friendly AEW&C through datalinking is one thing, but having the AEW&C able to provide targeting data through datalink to the J-20's weapons itself is another (the latter being a capability which we've suspected is in place for years, for missiles like PL-15 and PL-17 etc).
That said it's unrealistic to expect that kind of information to be provided clearly through official sources anyhow.