I have no doubt the xG will improve over time.
Agreed. When a team is outperforming their xG, in other words their strikers are converting difficult chances and goalkeepers are saving big chances, one of the two things can happen, they can either improve their performance i.e. reduce the xG differential, like Leicester did in the second half of their title winning season, or reality comes crashing down and actual results start to show the underlying problems like what happened to us under Emery.
I think Arteta has implemented systems and patterns so far where improvement in personnel will lead to a much higher improvement in actual performance.
Right now we are lacking in midfield in terms of chance creation, goal scoring and athletic ability which is why we play with two strikers which means we also need to play wing backs for width and a back 3 to make the middle of the pitch congested to stop shots etc.
I trust in Arteta to improve our shot creation and shot concession stats too especially with the right personnel.