IIRC the cockpit transcripts showed both pilots were at fault.
The transcript recorded the senior (2nd) pilot settling in his seat but did not record him saying "I have control" or the junior (3rd) pilot saying "You have control" in response.
This is the normal control handover dialogue which I'd expect any time control passes from the flying pilot to the non-flying pilot. Since there is no physical connection between the two sidestick controllers and no simulated control load feedback in that Airbus model, neither pilot could feel what the other was doing.