This is possible for the filming of the video, but I’m pretty sure that the intent of the maker is to showcase ability of advanced drones to coordinate/cooperate with manned combat aircraft. In tactically useful situations a second passenger is the still preferred controller option over pilot or ground based control, the latter by the virtue of proximity to combat zone so reduced delay in communications/greater resistance to interference.
I don't think you've read what I've written at all.
The point of what I've written is that a single seat aircraft can still be highly capable of commands in complex tactical environments. Just because a twin seater is even more capable of it doesn't detract from single seater capability, and whether it makes sense for a single or twin seater to be operating, depends on the complexity of the environment, the importance of the mission, extent of supporting assets.
A single seat J-20A might be able to control 8 drones in a tactically complex scenario, while a J-20S might be able to control 20, for example.
In such a scenario, is it even worth talking about a single seat vanilla J-20 doing a simple formation flight with a GJ-11 under its command?