The FA couldn't do anything other than warn him as the match officials took no action.
For me I don't like to see the referee coming over for a chat / warning when there is a 4th official, certainly not when the 4th official is one of the most experienced referees in the country and a FIFA Elite referee until very recently. I'm supportive of this when there is no 4th man and the senior AR is getting it in the neck, but at this level the 4th official needs to manage it himself and if it goes beyond his tolerance level the offender should be getting removed, not spoken to.
For me I don't like to see the referee coming over for a chat / warning when there is a 4th official, certainly not when the 4th official is one of the most experienced referees in the country and a FIFA Elite referee until very recently. I'm supportive of this when there is no 4th man and the senior AR is getting it in the neck, but at this level the 4th official needs to manage it himself and if it goes beyond his tolerance level the offender should be getting removed, not spoken to.