Thats what i want to say.
I mean that he is defensive not as a defender.. but as a midfielder able to go with the ball , but whos real focus is to box to box and tackle everyone around.
IMO, his real strenght is his presence on the field and his physicality, but also cann help the team going forward when needed, as he is not a Sissocko who was like chiellini, terribad going with the ball. CHiello is kind of ok because he is a defender... but as a midfielder is imperative that you have an accepable level of technique. Thats why i just do not liked sissock at all.
The thing is, he (Asa) is not supper effective when forced to do more offensive oriented duties like dribbling past constantly, or doing pinpoint crosses. Thats when his issues arise, because we are strectching at his capabilities. Conte is forcing him, and we are asking too much for a player who is not playing to his strenghts.
Like you say, im pretty sure he would be an awesome box to box... specially when chasing and closing down incoming opponents.
He is , to me, a box to box midfielder , who his main strenght is his physicality , but has the minimal technique and discipline required to be able to add whats needed when going on the offensive.
Still, i think his main strentght is on defensive duties and Conte is just asking him to do things he is not supposed to.
I even dont mind him playing as a LWB from time to time... cuz there are some situations that could demand it. But not as the first option when looking for goals