Those settings are only for when he takes charge of a game in your place. You have the final word, so his preference of play has no bearing. All staff have these presets in the event they are in charge of a team.
I'm not sure it always implemented though. Just check how your U19/reserves sides play in comparison to the coach preferences. If the coach you have selected to take charge of U19s prefers 4-3-3 then they should play that, assuming you haven't stated to use current match tactics.
Try different Assistant Managers - instead just changing their attributes with an editor.
Try an Ass Man with poor media and ask them to do press conferences - I had an Assman with poor media before and he upset my star player when he got injured by telling the media "it wasn't a big loss and lots of players could fill his role" - which wasn't true. The player got upset and took about a season to get his morale back up.
I refer you to my previous post. Obviously if an AssMan has all his attributes set to minmum then he'll have poor media. It makes no difference. You'd like to think it does and perhaps you are brainwashed into thinking it does but alas it doesn't.
Try as I've suggested. There will be differences due to the nature of computers and random events but adjust all his attributes to max then redo the same season with all attributes set to min.