In his pre-tournament briefing, Roberto Rosetti, UEFA's head of referees, gave specific examples of handball penalties -- for and against. Rosetti showed a clip of the ball hitting a defender's arm from a shot on goal. The arm was in a vertical position, close to the body.
Rosetti said: "Not every touch of arm, hand is a penalty. We want to consider the movement of the players. Biomechanical movements. You know, this is a clear situation. This is never a penalty."
The example given was very close to the Cucurella incident. While handball in UEFA competitions remains more strict, it has tried to give at least some more leeway to defenders so they don't need to have their hand behind their back.
So UEFA says that a defender in a standing position when the ball hits their arm at or close to their side, in position vertically, and/or with the arm behind the line of the body, it should not be punished. That Cucurella was bringing his arm in is a factor, as that's deemed to be removing a possible barrier
) we are essentially back to accidental or deliberate.