I see the opposite. Son sometimes ignores the opponent’s right back pushing up, Johnson goes with the opponent’s left back when he pushes forward. If the full back doesn’t join the attack then the winger doesn’t come back to defend. That is clearly the instruction from the manager.
At the game yesterday a bloke behind me was constantly berating Johnson (was it you Bishop?
) for not defending when it was Joelinton pulling across to try to cause the numerical overload on Porro.
There was an occasion yesterday only 2 minutes after Son had come on when Son’s direct opponent joined the attack and Son stood there for a few seconds before casually jogging back. He either doesn’t know who he is supposed to be defending against or doesn’t care.