4th officials at senior levels are generally told to be sensible and low touch with managers. The argument is that you need to use your authority when it is most needed, for example confrontations or serious breaches, and if you have been telling managers off all game for stepping out of the TA you will have lost some of that authority. Obviously if the manager is getting in the way of the assistant or risking getting involved in play you need to step in, but otherwise leave them to it.
When I first got onto the Conference I was told the same in my first game as 4th official, and that was endorsed by the assessor. Just stand between the two benches and only get involved when you need to, don't be fussy. Then when I dropped back to L5 I was panned by the assessor in my first game as senior assistant for the home team manager being out of his technical area too often ..! Different levels, different expectations.